Oil pressure dropping at operating temperature.


Jerry Marstall
 

That’s my problem – On initial start oil pressure is 40.  After oil temp approaches 140-180, the oil pressure works its way down to 25-30 and remains there.   At Keith’s Spring fling I brought up this problem and the consensus was it is either the gauge or the sensor.  I swapped in new ones and no improvement.  Sam pointed me to a source (see extract below) with a proposed solution that I would obviously like to avoid.  Before I leap into the money pit, does anyone have suggestions that I should pursue first?

Oil Pressure Drop at Operating Temperature

I have a J3 with a C-85 built up with the O-200 Crank, Rods, Pistons, and cylinders.The engine has roughly 700 smoh and recently it started losing oil pressure as the oil temp reaches 140 F.As the oil temp rises the oil pressure falls until the oil pressure reaches about 12 PSI.My mechanic has tried everything he can think of. I am sorry to say that we did a bottom end on the engine (turned the crank and replaced the main bearings) only to find that the problem still exists.I read the section of your QA where someone had a cracked lifter body that caused a loss of oil pressure.Do you think that this could be my problem as well?Any help would be greatly appreciated as the downtime and maintenance bills are getting pretty extensive at this point.

About half the questions I answer regard low oil pressure on these little Continentals.

If the crank has been machined and matched to new rod and main bearings, we can reasonably take that part of the system out of consideration.This narrows it down to other parts of the pressure system.

A cracked tappet body might contribute to low oil pressure, but this would not be a subtle problem to discover.A typical problem is that the little cup which fits into the tappet body pops out and gets wedged between the pushrod and the tappet body.Usually, the pushrod bends and the engine runs poorly, among other problems.

I did have an operator report that the bores for the tappet bodies in the crankcase were worn and ovaled which led to low overall oil pressure.I have not confirmed that this can result in low oil pressure since the bores are not pressure fed.But, the report came from a reputable source.

If I were to wager, I'd bet that the problem is more likely with the oil pump in the accessory case.This is a chronic weak spot with the little Continentals.If the tolerances are marginal, the engine will produce acceptable pressure, but as the engine warms, the tolerances open up and the pump loses pressure.I just fixed up a friend's C-85-12 installed on a Cessna 140 which exhibited exactly the same problem.We installed a new manufacture accessory case and the problem was fixed.

The oil pump consists of two gears, a cover plate and the oil pump cavity which is cast integral into the accessory case.If the oil pump bores become worn or grooved, the edge clearance between the oil pump gears and the becomes too great and the pump can't maintain pressure.The shaft holes for the pump gears also wear and pressure is lost.Finally, the cover plate can warp and oil will leak past causing low oil pressure.

So, my feeling is that the problem is probably with the oil pump in the accessory case.It is a fairly involved job to remove the accessory case, but no way around it.

You don't mention if you have a -8 or -12 engine, but here is the summary. The -8 case is magnesium and requires very special techniques to repair. Pretty much, the only place to get this work done is Drake Air, Tulsa, OK. www.DrakeAir.com, 918-445-3545.If the engine is a -12, then new cases are available for pretty reasonable cost (for airplane parts) from Mattituck, Edgecumbe G&N and others.My friend's case cost about $750 and another $150 for other parts along with about four hours of our free labor.

If you take a read through the Engine archive at the Fly Baby website, you will find that the accessory case is probably the number one problem with all Continentals.

 

 


Corbin <c_geiser@...>
 
Edited

Jerry,
 
That is my typical oil pressure when I am hot in the summer.  I am no A&P but 25 psi is still in the green for a O-200A, I believe.  I remember two summers ago, the O-200 forums were telling me that if my oil psi was in line with my rpm then all was well if still in the green.  Example, 2400 rpm could yield 24 psi at these hotter summer temps.  Of course, the weight of oil used can make a difference as well.  Are you running 50W or 100W?
 
Now that I have more precise digital engine instruments I am hoping for more accurate measurements.  But too hot to fly for me these days.
 
Again, I am no A&P so please don’t take my info to heart all on its own.
 
Corbin


On Jul 14, 2022, at 5:54 PM, Jerry Marstall <jerrylm1986@...> wrote:
That’s my problem – On initial start oil pressure is 40.  After oil temp approaches 140-180, the oil pressure works its way down to 25-30 and remains there.   At Keith’s Spring fling I brought up this problem and the consensus was it is either the gauge or the sensor.  I swapped in new ones and no improvement.  Sam pointed me to a source (see extract below) with a proposed solution that I would obviously like to avoid.  Before I leap into the money pit, does anyone have suggestions that I should pursue first?
Oil Pressure Drop at Operating Temperature
I have a J3 with a C-85 built up with the O-200 Crank, Rods, Pistons, and cylinders.The engine has roughly 700 smoh and recently it started losing oil pressure as the oil temp reaches 140 F.As the oil temp rises the oil pressure falls until the oil pressure reaches about 12 PSI.My mechanic has tried everything he can think of. I am sorry to say that we did a bottom end on the engine (turned the crank and replaced the main bearings) only to find that the problem still exists.I read the section of your QA where someone had a cracked lifter body that caused a loss of oil pressure.Do you think that this could be my problem as well?Any help would be greatly appreciated as the downtime and maintenance bills are getting pretty extensive at this point.
About half the questions I answer regard low oil pressure on these little Continentals.
If the crank has been machined and matched to new rod and main bearings, we can reasonably take that part of the system out of consideration.This narrows it down to other parts of the pressure system.
A cracked tappet body might contribute to low oil pressure, but this would not be a subtle problem to discover.A typical problem is that the little cup which fits into the tappet body pops out and gets wedged between the pushrod and the tappet body.Usually, the pushrod bends and the engine runs poorly, among other problems.
I did have an operator report that the bores for the tappet bodies in the crankcase were worn and ovaled which led to low overall oil pressure.I have not confirmed that this can result in low oil pressure since the bores are not pressure fed.But, the report came from a reputable source.
If I were to wager, I'd bet that the problem is more likely with the oil pump in the accessory case.This is a chronic weak spot with the little Continentals.If the tolerances are marginal, the engine will produce acceptable pressure, but as the engine warms, the tolerances open up and the pump loses pressure.I just fixed up a friend's C-85-12 installed on a Cessna 140 which exhibited exactly the same problem.We installed a new manufacture accessory case and the problem was fixed.
The oil pump consists of two gears, a cover plate and the oil pump cavity which is cast integral into the accessory case.If the oil pump bores become worn or grooved, the edge clearance between the oil pump gears and the becomes too great and the pump can't maintain pressure.The shaft holes for the pump gears also wear and pressure is lost.Finally, the cover plate can warp and oil will leak past causing low oil pressure.
So, my feeling is that the problem is probably with the oil pump in the accessory case.It is a fairly involved job to remove the accessory case, but no way around it.
You don't mention if you have a -8 or -12 engine, but here is the summary. The -8 case is magnesium and requires very special techniques to repair. Pretty much, the only place to get this work done is Drake Air, Tulsa, OK. www.DrakeAir.com, 918-445-3545.If the engine is a -12, then new cases are available for pretty reasonable cost (for airplane parts) from Mattituck, Edgecumbe G&N and others.My friend's case cost about $750 and another $150 for other parts along with about four hours of our free labor.
If you take a read through the Engine archive at the Fly Baby website, you will find that the accessory case is probably the number one problem with all Continentals.
 
 

--

Corbin 
N121CG


Jay Scheevel
 

Hi Jerry,

 

I have no experience with the Continental except flying behind them, but we do see this problem from time to time on the Jabirus and it is due to wear on the gearotors pump and housing. In the case of the Jab it is an easy thing to check and repair as the whole pump assembly is behind a single cover on the front of the engine held in place by 4 bolts. A 10 minute operation to have a look. I did not know that the entire accessory housing had to come off to access the pump on the O-200…sounds inconvenient.  Anyway, the symptoms sound reasonable based on the snippet that Sam put you on to.

 

Cheers,

Jay

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Jerry Marstall
Sent: Thursday, July 14, 2022 4:54 PM
To: Q-email list <main@Q-list.groups.io>
Subject: [Q-List] Oil pressure dropping at operating temperature.

 

That’s my problem – On initial start oil pressure is 40.  After oil temp approaches 140-180, the oil pressure works its way down to 25-30 and remains there.   At Keith’s Spring fling I brought up this problem and the consensus was it is either the gauge or the sensor.  I swapped in new ones and no improvement.  Sam pointed me to a source (see extract below) with a proposed solution that I would obviously like to avoid.  Before I leap into the money pit, does anyone have suggestions that I should pursue first?

Oil Pressure Drop at Operating Temperature

I have a J3 with a C-85 built up with the O-200 Crank, Rods, Pistons, and cylinders.The engine has roughly 700 smoh and recently it started losing oil pressure as the oil temp reaches 140 F.As the oil temp rises the oil pressure falls until the oil pressure reaches about 12 PSI.My mechanic has tried everything he can think of. I am sorry to say that we did a bottom end on the engine (turned the crank and replaced the main bearings) only to find that the problem still exists.I read the section of your QA where someone had a cracked lifter body that caused a loss of oil pressure.Do you think that this could be my problem as well?Any help would be greatly appreciated as the downtime and maintenance bills are getting pretty extensive at this point.

About half the questions I answer regard low oil pressure on these little Continentals.

If the crank has been machined and matched to new rod and main bearings, we can reasonably take that part of the system out of consideration.This narrows it down to other parts of the pressure system.

A cracked tappet body might contribute to low oil pressure, but this would not be a subtle problem to discover.A typical problem is that the little cup which fits into the tappet body pops out and gets wedged between the pushrod and the tappet body.Usually, the pushrod bends and the engine runs poorly, among other problems.

I did have an operator report that the bores for the tappet bodies in the crankcase were worn and ovaled which led to low overall oil pressure.I have not confirmed that this can result in low oil pressure since the bores are not pressure fed.But, the report came from a reputable source.

If I were to wager, I'd bet that the problem is more likely with the oil pump in the accessory case.This is a chronic weak spot with the little Continentals.If the tolerances are marginal, the engine will produce acceptable pressure, but as the engine warms, the tolerances open up and the pump loses pressure.I just fixed up a friend's C-85-12 installed on a Cessna 140 which exhibited exactly the same problem.We installed a new manufacture accessory case and the problem was fixed.

The oil pump consists of two gears, a cover plate and the oil pump cavity which is cast integral into the accessory case.If the oil pump bores become worn or grooved, the edge clearance between the oil pump gears and the becomes too great and the pump can't maintain pressure.The shaft holes for the pump gears also wear and pressure is lost.Finally, the cover plate can warp and oil will leak past causing low oil pressure.

So, my feeling is that the problem is probably with the oil pump in the accessory case.It is a fairly involved job to remove the accessory case, but no way around it.

You don't mention if you have a -8 or -12 engine, but here is the summary. The -8 case is magnesium and requires very special techniques to repair. Pretty much, the only place to get this work done is Drake Air, Tulsa, OK. www.DrakeAir.com, 918-445-3545.If the engine is a -12, then new cases are available for pretty reasonable cost (for airplane parts) from Mattituck, Edgecumbe G&N and others.My friend's case cost about $750 and another $150 for other parts along with about four hours of our free labor.

If you take a read through the Engine archive at the Fly Baby website, you will find that the accessory case is probably the number one problem with all Continentals.

 

 


Sandaircraft
 

Ive had problems with cheap oil, wont mention type but its 20w50. That stuff is like water. Ive seen o200s and o470s loose prime after sitting for a while, then not be able to pick it back up and the pump needs prime. Switched oil and issue gone.
Also remember as the oil heats up it becomes thinner thus lower oil pressure.  If its still in the green i wouldnt worry too much about it. Just monitor, if it keeps dropping lower and lower then start searching for an issue.


On Jul 14, 2022, at 7:13 PM, Jay Scheevel <jay@...> wrote:



Hi Jerry,

 

I have no experience with the Continental except flying behind them, but we do see this problem from time to time on the Jabirus and it is due to wear on the gearotors pump and housing. In the case of the Jab it is an easy thing to check and repair as the whole pump assembly is behind a single cover on the front of the engine held in place by 4 bolts. A 10 minute operation to have a look. I did not know that the entire accessory housing had to come off to access the pump on the O-200…sounds inconvenient.  Anyway, the symptoms sound reasonable based on the snippet that Sam put you on to.

 

Cheers,

Jay

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Jerry Marstall
Sent: Thursday, July 14, 2022 4:54 PM
To: Q-email list <main@Q-list.groups.io>
Subject: [Q-List] Oil pressure dropping at operating temperature.

 

That’s my problem – On initial start oil pressure is 40.  After oil temp approaches 140-180, the oil pressure works its way down to 25-30 and remains there.   At Keith’s Spring fling I brought up this problem and the consensus was it is either the gauge or the sensor.  I swapped in new ones and no improvement.  Sam pointed me to a source (see extract below) with a proposed solution that I would obviously like to avoid.  Before I leap into the money pit, does anyone have suggestions that I should pursue first?

Oil Pressure Drop at Operating Temperature

I have a J3 with a C-85 built up with the O-200 Crank, Rods, Pistons, and cylinders.The engine has roughly 700 smoh and recently it started losing oil pressure as the oil temp reaches 140 F.As the oil temp rises the oil pressure falls until the oil pressure reaches about 12 PSI.My mechanic has tried everything he can think of. I am sorry to say that we did a bottom end on the engine (turned the crank and replaced the main bearings) only to find that the problem still exists.I read the section of your QA where someone had a cracked lifter body that caused a loss of oil pressure.Do you think that this could be my problem as well?Any help would be greatly appreciated as the downtime and maintenance bills are getting pretty extensive at this point.

About half the questions I answer regard low oil pressure on these little Continentals.

If the crank has been machined and matched to new rod and main bearings, we can reasonably take that part of the system out of consideration.This narrows it down to other parts of the pressure system.

A cracked tappet body might contribute to low oil pressure, but this would not be a subtle problem to discover.A typical problem is that the little cup which fits into the tappet body pops out and gets wedged between the pushrod and the tappet body.Usually, the pushrod bends and the engine runs poorly, among other problems.

I did have an operator report that the bores for the tappet bodies in the crankcase were worn and ovaled which led to low overall oil pressure.I have not confirmed that this can result in low oil pressure since the bores are not pressure fed.But, the report came from a reputable source.

If I were to wager, I'd bet that the problem is more likely with the oil pump in the accessory case.This is a chronic weak spot with the little Continentals.If the tolerances are marginal, the engine will produce acceptable pressure, but as the engine warms, the tolerances open up and the pump loses pressure.I just fixed up a friend's C-85-12 installed on a Cessna 140 which exhibited exactly the same problem.We installed a new manufacture accessory case and the problem was fixed.

The oil pump consists of two gears, a cover plate and the oil pump cavity which is cast integral into the accessory case.If the oil pump bores become worn or grooved, the edge clearance between the oil pump gears and the becomes too great and the pump can't maintain pressure.The shaft holes for the pump gears also wear and pressure is lost.Finally, the cover plate can warp and oil will leak past causing low oil pressure.

So, my feeling is that the problem is probably with the oil pump in the accessory case.It is a fairly involved job to remove the accessory case, but no way around it.

You don't mention if you have a -8 or -12 engine, but here is the summary. The -8 case is magnesium and requires very special techniques to repair. Pretty much, the only place to get this work done is Drake Air, Tulsa, OK. www.DrakeAir.com, 918-445-3545.If the engine is a -12, then new cases are available for pretty reasonable cost (for airplane parts) from Mattituck, Edgecumbe G&N and others.My friend's case cost about $750 and another $150 for other parts along with about four hours of our free labor.

If you take a read through the Engine archive at the Fly Baby website, you will find that the accessory case is probably the number one problem with all Continentals.

 

 


Chris Walterson
 

One other thing about oil pressure difference, is, does the airplane have an oil filter kit.  I have seen oil filters that have caused lower pressures. .

 On a Lycoming i have if you want more oil pressure you install a AN3 washer behind the spring and presto, more oil pressure.

 Take care----------  Chris


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Corbin <c_geiser@...>
 

Good point, Chris….that reminds me that O-200’s have an oil adjustment screw on rear of case. I’ve never adjusted it though.

Corbin

On Jul 14, 2022, at 6:34 PM, Chris Walterson <dkeats@...> wrote:

 One other thing about oil pressure difference, is, does the airplane have an oil filter kit. I have seen oil filters that have caused lower pressures. .

On a Lycoming i have if you want more oil pressure you install a AN3 washer behind the spring and presto, more oil pressure.

Take care---------- Chris


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--
Corbin
N121CG


Jay Scheevel
 

Jerry,

 

Thought of something else. Do  you have an oil cooler and is it “downstream” from your oil pump but “upstream” from the pressure sensor?  If so, then the oil filter could, over a period of time, start to get clogged and start to soak up more pressure prior to the sensor seeing it. Just a thought. Maybe a good cleaning of your oil cooler would do the trick.

 

Cheers,

Jay

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Jerry Marstall
Sent: Thursday, July 14, 2022 4:54 PM
To: Q-email list <main@Q-list.groups.io>
Subject: [Q-List] Oil pressure dropping at operating temperature.

 

That’s my problem – On initial start oil pressure is 40.  After oil temp approaches 140-180, the oil pressure works its way down to 25-30 and remains there.   At Keith’s Spring fling I brought up this problem and the consensus was it is either the gauge or the sensor.  I swapped in new ones and no improvement.  Sam pointed me to a source (see extract below) with a proposed solution that I would obviously like to avoid.  Before I leap into the money pit, does anyone have suggestions that I should pursue first?

Oil Pressure Drop at Operating Temperature

I have a J3 with a C-85 built up with the O-200 Crank, Rods, Pistons, and cylinders.The engine has roughly 700 smoh and recently it started losing oil pressure as the oil temp reaches 140 F.As the oil temp rises the oil pressure falls until the oil pressure reaches about 12 PSI.My mechanic has tried everything he can think of. I am sorry to say that we did a bottom end on the engine (turned the crank and replaced the main bearings) only to find that the problem still exists.I read the section of your QA where someone had a cracked lifter body that caused a loss of oil pressure.Do you think that this could be my problem as well?Any help would be greatly appreciated as the downtime and maintenance bills are getting pretty extensive at this point.

About half the questions I answer regard low oil pressure on these little Continentals.

If the crank has been machined and matched to new rod and main bearings, we can reasonably take that part of the system out of consideration.This narrows it down to other parts of the pressure system.

A cracked tappet body might contribute to low oil pressure, but this would not be a subtle problem to discover.A typical problem is that the little cup which fits into the tappet body pops out and gets wedged between the pushrod and the tappet body.Usually, the pushrod bends and the engine runs poorly, among other problems.

I did have an operator report that the bores for the tappet bodies in the crankcase were worn and ovaled which led to low overall oil pressure.I have not confirmed that this can result in low oil pressure since the bores are not pressure fed.But, the report came from a reputable source.

If I were to wager, I'd bet that the problem is more likely with the oil pump in the accessory case.This is a chronic weak spot with the little Continentals.If the tolerances are marginal, the engine will produce acceptable pressure, but as the engine warms, the tolerances open up and the pump loses pressure.I just fixed up a friend's C-85-12 installed on a Cessna 140 which exhibited exactly the same problem.We installed a new manufacture accessory case and the problem was fixed.

The oil pump consists of two gears, a cover plate and the oil pump cavity which is cast integral into the accessory case.If the oil pump bores become worn or grooved, the edge clearance between the oil pump gears and the becomes too great and the pump can't maintain pressure.The shaft holes for the pump gears also wear and pressure is lost.Finally, the cover plate can warp and oil will leak past causing low oil pressure.

So, my feeling is that the problem is probably with the oil pump in the accessory case.It is a fairly involved job to remove the accessory case, but no way around it.

You don't mention if you have a -8 or -12 engine, but here is the summary. The -8 case is magnesium and requires very special techniques to repair. Pretty much, the only place to get this work done is Drake Air, Tulsa, OK. www.DrakeAir.com, 918-445-3545.If the engine is a -12, then new cases are available for pretty reasonable cost (for airplane parts) from Mattituck, Edgecumbe G&N and others.My friend's case cost about $750 and another $150 for other parts along with about four hours of our free labor.

If you take a read through the Engine archive at the Fly Baby website, you will find that the accessory case is probably the number one problem with all Continentals.

 

 


Jerry Marstall
 

Thx Corbin.  The Continental specs list normal oil pressure as 30-60.

Hey gang, what are some of your readings?


On Thu, Jul 14, 2022, 7:01 PM Corbin via groups.io <c_geiser=icloud.com@groups.io> wrote:
Jerry,

That is my typical oil pressure when I am hot in the summer.  I am no A&P but 25 psi is still in the green for a O-200A, I believe.  I remember two summers ago, the O-200 forums were telling me that if my oil psi was in line with my rpm then all was well if still in the green.  Example, 2400 rpm could yield 24 psi at these hotter summer temps.  Of course, the weight of oil used can make a difference as well.  Are you running 50W or 100W?

Now that I have more price digital engine instruments I am hoping for more accurate measurements.  But too hot to fly for me these days.

Again, I am no A&P so please don’t take my info to heart all on its own.

Corbin


On Jul 14, 2022, at 5:54 PM, Jerry Marstall <jerrylm1986@...> wrote:

That’s my problem – On initial start oil pressure is 40.  After oil temp approaches 140-180, the oil pressure works its way down to 25-30 and remains there.   At Keith’s Spring fling I brought up this problem and the consensus was it is either the gauge or the sensor.  I swapped in new ones and no improvement.  Sam pointed me to a source (see extract below) with a proposed solution that I would obviously like to avoid.  Before I leap into the money pit, does anyone have suggestions that I should pursue first?
Oil Pressure Drop at Operating Temperature
I have a J3 with a C-85 built up with the O-200 Crank, Rods, Pistons, and cylinders.The engine has roughly 700 smoh and recently it started losing oil pressure as the oil temp reaches 140 F.As the oil temp rises the oil pressure falls until the oil pressure reaches about 12 PSI.My mechanic has tried everything he can think of. I am sorry to say that we did a bottom end on the engine (turned the crank and replaced the main bearings) only to find that the problem still exists.I read the section of your QA where someone had a cracked lifter body that caused a loss of oil pressure.Do you think that this could be my problem as well?Any help would be greatly appreciated as the downtime and maintenance bills are getting pretty extensive at this point.
About half the questions I answer regard low oil pressure on these little Continentals.
If the crank has been machined and matched to new rod and main bearings, we can reasonably take that part of the system out of consideration.This narrows it down to other parts of the pressure system.
A cracked tappet body might contribute to low oil pressure, but this would not be a subtle problem to discover.A typical problem is that the little cup which fits into the tappet body pops out and gets wedged between the pushrod and the tappet body.Usually, the pushrod bends and the engine runs poorly, among other problems.
I did have an operator report that the bores for the tappet bodies in the crankcase were worn and ovaled which led to low overall oil pressure.I have not confirmed that this can result in low oil pressure since the bores are not pressure fed.But, the report came from a reputable source.
If I were to wager, I'd bet that the problem is more likely with the oil pump in the accessory case.This is a chronic weak spot with the little Continentals.If the tolerances are marginal, the engine will produce acceptable pressure, but as the engine warms, the tolerances open up and the pump loses pressure.I just fixed up a friend's C-85-12 installed on a Cessna 140 which exhibited exactly the same problem.We installed a new manufacture accessory case and the problem was fixed.
The oil pump consists of two gears, a cover plate and the oil pump cavity which is cast integral into the accessory case.If the oil pump bores become worn or grooved, the edge clearance between the oil pump gears and the becomes too great and the pump can't maintain pressure.The shaft holes for the pump gears also wear and pressure is lost.Finally, the cover plate can warp and oil will leak past causing low oil pressure.
So, my feeling is that the problem is probably with the oil pump in the accessory case.It is a fairly involved job to remove the accessory case, but no way around it.
You don't mention if you have a -8 or -12 engine, but here is the summary. The -8 case is magnesium and requires very special techniques to repair. Pretty much, the only place to get this work done is Drake Air, Tulsa, OK. www.DrakeAir.com, 918-445-3545.If the engine is a -12, then new cases are available for pretty reasonable cost (for airplane parts) from Mattituck, Edgecumbe G&N and others.My friend's case cost about $750 and another $150 for other parts along with about four hours of our free labor.
If you take a read through the Engine archive at the Fly Baby website, you will find that the accessory case is probably the number one problem with all Continentals.
 
 


--

Corbin 
N121CG


Kevin Boddicker
 

Jerry,
Mine is 40psi+ on start up. Maintains that at cruse rpm 2450, temp has no bearing.
When hot, at idle, about 20psi. I’ve been told this is normal. 
The only thing that is odd, if my prop is turned at all, I might loose prime.
So NOBODY touches my prop!
If not touched I can go months and all is good.
If prime is lose, I have to take off the oil filter and back prime the system.
Also when changing oil, I back prime.

That’s my story.

Kevin



On Jul 14, 2022, at 9:31 PM, Jerry Marstall <jerrylm1986@...> wrote:


Thx Corbin.  The Continental specs list normal oil pressure as 30-60.

Hey gang, what are some of your readings?


On Thu, Jul 14, 2022, 7:01 PM Corbin via groups.io <c_geiser=icloud.com@groups.io> wrote:
Jerry,

That is my typical oil pressure when I am hot in the summer.  I am no A&P but 25 psi is still in the green for a O-200A, I believe.  I remember two summers ago, the O-200 forums were telling me that if my oil psi was in line with my rpm then all was well if still in the green.  Example, 2400 rpm could yield 24 psi at these hotter summer temps.  Of course, the weight of oil used can make a difference as well.  Are you running 50W or 100W?

Now that I have more price digital engine instruments I am hoping for more accurate measurements.  But too hot to fly for me these days.

Again, I am no A&P so please don’t take my info to heart all on its own.

Corbin


On Jul 14, 2022, at 5:54 PM, Jerry Marstall <jerrylm1986@...> wrote:

That’s my problem – On initial start oil pressure is 40.  After oil temp approaches 140-180, the oil pressure works its way down to 25-30 and remains there.   At Keith’s Spring fling I brought up this problem and the consensus was it is either the gauge or the sensor.  I swapped in new ones and no improvement.  Sam pointed me to a source (see extract below) with a proposed solution that I would obviously like to avoid.  Before I leap into the money pit, does anyone have suggestions that I should pursue first?
Oil Pressure Drop at Operating Temperature
I have a J3 with a C-85 built up with the O-200 Crank, Rods, Pistons, and cylinders.The engine has roughly 700 smoh and recently it started losing oil pressure as the oil temp reaches 140 F.As the oil temp rises the oil pressure falls until the oil pressure reaches about 12 PSI.My mechanic has tried everything he can think of. I am sorry to say that we did a bottom end on the engine (turned the crank and replaced the main bearings) only to find that the problem still exists.I read the section of your QA where someone had a cracked lifter body that caused a loss of oil pressure.Do you think that this could be my problem as well?Any help would be greatly appreciated as the downtime and maintenance bills are getting pretty extensive at this point.
About half the questions I answer regard low oil pressure on these little Continentals.
If the crank has been machined and matched to new rod and main bearings, we can reasonably take that part of the system out of consideration.This narrows it down to other parts of the pressure system.
A cracked tappet body might contribute to low oil pressure, but this would not be a subtle problem to discover.A typical problem is that the little cup which fits into the tappet body pops out and gets wedged between the pushrod and the tappet body.Usually, the pushrod bends and the engine runs poorly, among other problems.
I did have an operator report that the bores for the tappet bodies in the crankcase were worn and ovaled which led to low overall oil pressure.I have not confirmed that this can result in low oil pressure since the bores are not pressure fed.But, the report came from a reputable source.
If I were to wager, I'd bet that the problem is more likely with the oil pump in the accessory case.This is a chronic weak spot with the little Continentals.If the tolerances are marginal, the engine will produce acceptable pressure, but as the engine warms, the tolerances open up and the pump loses pressure.I just fixed up a friend's C-85-12 installed on a Cessna 140 which exhibited exactly the same problem.We installed a new manufacture accessory case and the problem was fixed.
The oil pump consists of two gears, a cover plate and the oil pump cavity which is cast integral into the accessory case.If the oil pump bores become worn or grooved, the edge clearance between the oil pump gears and the becomes too great and the pump can't maintain pressure.The shaft holes for the pump gears also wear and pressure is lost.Finally, the cover plate can warp and oil will leak past causing low oil pressure.
So, my feeling is that the problem is probably with the oil pump in the accessory case.It is a fairly involved job to remove the accessory case, but no way around it.
You don't mention if you have a -8 or -12 engine, but here is the summary. The -8 case is magnesium and requires very special techniques to repair. Pretty much, the only place to get this work done is Drake Air, Tulsa, OK. www.DrakeAir.com, 918-445-3545.If the engine is a -12, then new cases are available for pretty reasonable cost (for airplane parts) from Mattituck, Edgecumbe G&N and others.My friend's case cost about $750 and another $150 for other parts along with about four hours of our free labor.
If you take a read through the Engine archive at the Fly Baby website, you will find that the accessory case is probably the number one problem with all Continentals.
 
 


--

Corbin 
N121CG


Paul Fisher
 

You made me look!

Sorry for the delayed response Jerry, I have an old analog oil pressure gauge so I don't pay attention to the absolute value - I just verify the needle is in the correct position.  I had to come to the airport to see what value that position equated to!

My green arc is indeed 30-60 psi, and I tend to run about 30-35 most of the time.  As Kevin said, when it's hot and at idle it will drop to ~20, but will increase with an increase in RPM.

Having said all that I have never tried to calibrate the guage.  So I have no idea how accurate those numbers are.  I don't worry about oil pressure.  But then again I don't live in the mountains!  Where I fly there is usually a corn field within 15 to 20 feet of me!!

Good luck!

Paul 


On Thu, Jul 14, 2022, 21:31 Jerry Marstall <jerrylm1986@...> wrote:
Thx Corbin.  The Continental specs list normal oil pressure as 30-60.

Hey gang, what are some of your readings?


On Thu, Jul 14, 2022, 7:01 PM Corbin via groups.io <c_geiser=icloud.com@groups.io> wrote:
Jerry,

That is my typical oil pressure when I am hot in the summer.  I am no A&P but 25 psi is still in the green for a O-200A, I believe.  I remember two summers ago, the O-200 forums were telling me that if my oil psi was in line with my rpm then all was well if still in the green.  Example, 2400 rpm could yield 24 psi at these hotter summer temps.  Of course, the weight of oil used can make a difference as well.  Are you running 50W or 100W?

Now that I have more price digital engine instruments I am hoping for more accurate measurements.  But too hot to fly for me these days.

Again, I am no A&P so please don’t take my info to heart all on its own.

Corbin


On Jul 14, 2022, at 5:54 PM, Jerry Marstall <jerrylm1986@...> wrote:

That’s my problem – On initial start oil pressure is 40.  After oil temp approaches 140-180, the oil pressure works its way down to 25-30 and remains there.   At Keith’s Spring fling I brought up this problem and the consensus was it is either the gauge or the sensor.  I swapped in new ones and no improvement.  Sam pointed me to a source (see extract below) with a proposed solution that I would obviously like to avoid.  Before I leap into the money pit, does anyone have suggestions that I should pursue first?
Oil Pressure Drop at Operating Temperature
I have a J3 with a C-85 built up with the O-200 Crank, Rods, Pistons, and cylinders.The engine has roughly 700 smoh and recently it started losing oil pressure as the oil temp reaches 140 F.As the oil temp rises the oil pressure falls until the oil pressure reaches about 12 PSI.My mechanic has tried everything he can think of. I am sorry to say that we did a bottom end on the engine (turned the crank and replaced the main bearings) only to find that the problem still exists.I read the section of your QA where someone had a cracked lifter body that caused a loss of oil pressure.Do you think that this could be my problem as well?Any help would be greatly appreciated as the downtime and maintenance bills are getting pretty extensive at this point.
About half the questions I answer regard low oil pressure on these little Continentals.
If the crank has been machined and matched to new rod and main bearings, we can reasonably take that part of the system out of consideration.This narrows it down to other parts of the pressure system.
A cracked tappet body might contribute to low oil pressure, but this would not be a subtle problem to discover.A typical problem is that the little cup which fits into the tappet body pops out and gets wedged between the pushrod and the tappet body.Usually, the pushrod bends and the engine runs poorly, among other problems.
I did have an operator report that the bores for the tappet bodies in the crankcase were worn and ovaled which led to low overall oil pressure.I have not confirmed that this can result in low oil pressure since the bores are not pressure fed.But, the report came from a reputable source.
If I were to wager, I'd bet that the problem is more likely with the oil pump in the accessory case.This is a chronic weak spot with the little Continentals.If the tolerances are marginal, the engine will produce acceptable pressure, but as the engine warms, the tolerances open up and the pump loses pressure.I just fixed up a friend's C-85-12 installed on a Cessna 140 which exhibited exactly the same problem.We installed a new manufacture accessory case and the problem was fixed.
The oil pump consists of two gears, a cover plate and the oil pump cavity which is cast integral into the accessory case.If the oil pump bores become worn or grooved, the edge clearance between the oil pump gears and the becomes too great and the pump can't maintain pressure.The shaft holes for the pump gears also wear and pressure is lost.Finally, the cover plate can warp and oil will leak past causing low oil pressure.
So, my feeling is that the problem is probably with the oil pump in the accessory case.It is a fairly involved job to remove the accessory case, but no way around it.
You don't mention if you have a -8 or -12 engine, but here is the summary. The -8 case is magnesium and requires very special techniques to repair. Pretty much, the only place to get this work done is Drake Air, Tulsa, OK. www.DrakeAir.com, 918-445-3545.If the engine is a -12, then new cases are available for pretty reasonable cost (for airplane parts) from Mattituck, Edgecumbe G&N and others.My friend's case cost about $750 and another $150 for other parts along with about four hours of our free labor.
If you take a read through the Engine archive at the Fly Baby website, you will find that the accessory case is probably the number one problem with all Continentals.
 
 


--

Corbin 
N121CG


Bruce Crain
 

Kevin will turning up the rpms at start up bring the oil pressure up?  I have to do that if I haven’t flown in a month or so.
Bruce


On Jul 15, 2022, at 1:00 PM, Paul Fisher <rv7a.n18pf@...> wrote:


You made me look!

Sorry for the delayed response Jerry, I have an old analog oil pressure gauge so I don't pay attention to the absolute value - I just verify the needle is in the correct position.  I had to come to the airport to see what value that position equated to!

My green arc is indeed 30-60 psi, and I tend to run about 30-35 most of the time.  As Kevin said, when it's hot and at idle it will drop to ~20, but will increase with an increase in RPM.

Having said all that I have never tried to calibrate the guage.  So I have no idea how accurate those numbers are.  I don't worry about oil pressure.  But then again I don't live in the mountains!  Where I fly there is usually a corn field within 15 to 20 feet of me!!

Good luck!

Paul 

On Thu, Jul 14, 2022, 21:31 Jerry Marstall <jerrylm1986@...> wrote:
Thx Corbin.  The Continental specs list normal oil pressure as 30-60.

Hey gang, what are some of your readings?


On Thu, Jul 14, 2022, 7:01 PM Corbin via groups.io <c_geiser=icloud.com@groups.io> wrote:
Jerry,

That is my typical oil pressure when I am hot in the summer.  I am no A&P but 25 psi is still in the green for a O-200A, I believe.  I remember two summers ago, the O-200 forums were telling me that if my oil psi was in line with my rpm then all was well if still in the green.  Example, 2400 rpm could yield 24 psi at these hotter summer temps.  Of course, the weight of oil used can make a difference as well.  Are you running 50W or 100W?

Now that I have more price digital engine instruments I am hoping for more accurate measurements.  But too hot to fly for me these days.

Again, I am no A&P so please don’t take my info to heart all on its own.

Corbin


On Jul 14, 2022, at 5:54 PM, Jerry Marstall <jerrylm1986@...> wrote:

That’s my problem – On initial start oil pressure is 40.  After oil temp approaches 140-180, the oil pressure works its way down to 25-30 and remains there.   At Keith’s Spring fling I brought up this problem and the consensus was it is either the gauge or the sensor.  I swapped in new ones and no improvement.  Sam pointed me to a source (see extract below) with a proposed solution that I would obviously like to avoid.  Before I leap into the money pit, does anyone have suggestions that I should pursue first?
Oil Pressure Drop at Operating Temperature
I have a J3 with a C-85 built up with the O-200 Crank, Rods, Pistons, and cylinders.The engine has roughly 700 smoh and recently it started losing oil pressure as the oil temp reaches 140 F.As the oil temp rises the oil pressure falls until the oil pressure reaches about 12 PSI.My mechanic has tried everything he can think of. I am sorry to say that we did a bottom end on the engine (turned the crank and replaced the main bearings) only to find that the problem still exists.I read the section of your QA where someone had a cracked lifter body that caused a loss of oil pressure.Do you think that this could be my problem as well?Any help would be greatly appreciated as the downtime and maintenance bills are getting pretty extensive at this point.
About half the questions I answer regard low oil pressure on these little Continentals.
If the crank has been machined and matched to new rod and main bearings, we can reasonably take that part of the system out of consideration.This narrows it down to other parts of the pressure system.
A cracked tappet body might contribute to low oil pressure, but this would not be a subtle problem to discover.A typical problem is that the little cup which fits into the tappet body pops out and gets wedged between the pushrod and the tappet body.Usually, the pushrod bends and the engine runs poorly, among other problems.
I did have an operator report that the bores for the tappet bodies in the crankcase were worn and ovaled which led to low overall oil pressure.I have not confirmed that this can result in low oil pressure since the bores are not pressure fed.But, the report came from a reputable source.
If I were to wager, I'd bet that the problem is more likely with the oil pump in the accessory case.This is a chronic weak spot with the little Continentals.If the tolerances are marginal, the engine will produce acceptable pressure, but as the engine warms, the tolerances open up and the pump loses pressure.I just fixed up a friend's C-85-12 installed on a Cessna 140 which exhibited exactly the same problem.We installed a new manufacture accessory case and the problem was fixed.
The oil pump consists of two gears, a cover plate and the oil pump cavity which is cast integral into the accessory case.If the oil pump bores become worn or grooved, the edge clearance between the oil pump gears and the becomes too great and the pump can't maintain pressure.The shaft holes for the pump gears also wear and pressure is lost.Finally, the cover plate can warp and oil will leak past causing low oil pressure.
So, my feeling is that the problem is probably with the oil pump in the accessory case.It is a fairly involved job to remove the accessory case, but no way around it.
You don't mention if you have a -8 or -12 engine, but here is the summary. The -8 case is magnesium and requires very special techniques to repair. Pretty much, the only place to get this work done is Drake Air, Tulsa, OK. www.DrakeAir.com, 918-445-3545.If the engine is a -12, then new cases are available for pretty reasonable cost (for airplane parts) from Mattituck, Edgecumbe G&N and others.My friend's case cost about $750 and another $150 for other parts along with about four hours of our free labor.
If you take a read through the Engine archive at the Fly Baby website, you will find that the accessory case is probably the number one problem with all Continentals.
 
 


--

Corbin 
N121CG


Dave Dugas
 

Hi Jerry
Rule of thumb with the Revmaster is 10 lbs PSI for every 1000 RPM. Example....2500 RPM / 25 PSI oil pressure.


On Fri, Jul 15, 2022 at 2:31 PM, Bruce Crain
<jcrain2@...> wrote:
Kevin will turning up the rpms at start up bring the oil pressure up?  I have to do that if I haven’t flown in a month or so.
Bruce


On Jul 15, 2022, at 1:00 PM, Paul Fisher <rv7a.n18pf@...> wrote:


You made me look!

Sorry for the delayed response Jerry, I have an old analog oil pressure gauge so I don't pay attention to the absolute value - I just verify the needle is in the correct position.  I had to come to the airport to see what value that position equated to!

My green arc is indeed 30-60 psi, and I tend to run about 30-35 most of the time.  As Kevin said, when it's hot and at idle it will drop to ~20, but will increase with an increase in RPM.

Having said all that I have never tried to calibrate the guage.  So I have no idea how accurate those numbers are.  I don't worry about oil pressure.  But then again I don't live in the mountains!  Where I fly there is usually a corn field within 15 to 20 feet of me!!

Good luck!

Paul 

On Thu, Jul 14, 2022, 21:31 Jerry Marstall <jerrylm1986@...> wrote:
Thx Corbin.  The Continental specs list normal oil pressure as 30-60.

Hey gang, what are some of your readings?


On Thu, Jul 14, 2022, 7:01 PM Corbin via groups.io <c_geiser=icloud.com@groups.io> wrote:
Jerry,

That is my typical oil pressure when I am hot in the summer.  I am no A&P but 25 psi is still in the green for a O-200A, I believe.  I remember two summers ago, the O-200 forums were telling me that if my oil psi was in line with my rpm then all was well if still in the green.  Example, 2400 rpm could yield 24 psi at these hotter summer temps.  Of course, the weight of oil used can make a difference as well.  Are you running 50W or 100W?

Now that I have more price digital engine instruments I am hoping for more accurate measurements.  But too hot to fly for me these days.

Again, I am no A&P so please don’t take my info to heart all on its own.

Corbin


On Jul 14, 2022, at 5:54 PM, Jerry Marstall <jerrylm1986@...> wrote:

That’s my problem – On initial start oil pressure is 40.  After oil temp approaches 140-180, the oil pressure works its way down to 25-30 and remains there.   At Keith’s Spring fling I brought up this problem and the consensus was it is either the gauge or the sensor.  I swapped in new ones and no improvement.  Sam pointed me to a source (see extract below) with a proposed solution that I would obviously like to avoid.  Before I leap into the money pit, does anyone have suggestions that I should pursue first?
Oil Pressure Drop at Operating Temperature
I have a J3 with a C-85 built up with the O-200 Crank, Rods, Pistons, and cylinders.The engine has roughly 700 smoh and recently it started losing oil pressure as the oil temp reaches 140 F.As the oil temp rises the oil pressure falls until the oil pressure reaches about 12 PSI.My mechanic has tried everything he can think of. I am sorry to say that we did a bottom end on the engine (turned the crank and replaced the main bearings) only to find that the problem still exists.I read the section of your QA where someone had a cracked lifter body that caused a loss of oil pressure.Do you think that this could be my problem as well?Any help would be greatly appreciated as the downtime and maintenance bills are getting pretty extensive at this point.
About half the questions I answer regard low oil pressure on these little Continentals.
If the crank has been machined and matched to new rod and main bearings, we can reasonably take that part of the system out of consideration.This narrows it down to other parts of the pressure system.
A cracked tappet body might contribute to low oil pressure, but this would not be a subtle problem to discover.A typical problem is that the little cup which fits into the tappet body pops out and gets wedged between the pushrod and the tappet body.Usually, the pushrod bends and the engine runs poorly, among other problems.
I did have an operator report that the bores for the tappet bodies in the crankcase were worn and ovaled which led to low overall oil pressure.I have not confirmed that this can result in low oil pressure since the bores are not pressure fed.But, the report came from a reputable source.
If I were to wager, I'd bet that the problem is more likely with the oil pump in the accessory case.This is a chronic weak spot with the little Continentals.If the tolerances are marginal, the engine will produce acceptable pressure, but as the engine warms, the tolerances open up and the pump loses pressure.I just fixed up a friend's C-85-12 installed on a Cessna 140 which exhibited exactly the same problem.We installed a new manufacture accessory case and the problem was fixed.
The oil pump consists of two gears, a cover plate and the oil pump cavity which is cast integral into the accessory case.If the oil pump bores become worn or grooved, the edge clearance between the oil pump gears and the becomes too great and the pump can't maintain pressure.The shaft holes for the pump gears also wear and pressure is lost.Finally, the cover plate can warp and oil will leak past causing low oil pressure.
So, my feeling is that the problem is probably with the oil pump in the accessory case.It is a fairly involved job to remove the accessory case, but no way around it.
You don't mention if you have a -8 or -12 engine, but here is the summary. The -8 case is magnesium and requires very special techniques to repair. Pretty much, the only place to get this work done is Drake Air, Tulsa, OK. www.DrakeAir.com, 918-445-3545.If the engine is a -12, then new cases are available for pretty reasonable cost (for airplane parts) from Mattituck, Edgecumbe G&N and others.My friend's case cost about $750 and another $150 for other parts along with about four hours of our free labor.
If you take a read through the Engine archive at the Fly Baby website, you will find that the accessory case is probably the number one problem with all Continentals.
 
 


--

Corbin 
N121CG


Jerry Marstall
 

Kev and Dave, thx for your input. Kev, yours fit well within the specs.  The Revmaster must have a very efficient oil passage way.
Sam gave me an excellent reference.  It appears that this is a common Continental problem. Unfortunately, there is a plethora of possible causes.  Solutions range from relatively easy to engine teardown. Stay tuned. Jm

On Fri, Jul 15, 2022, 12:16 PM Kevin Boddicker <trumanst@...> wrote:
Jerry,
Mine is 40psi+ on start up. Maintains that at cruse rpm 2450, temp has no bearing.
When hot, at idle, about 20psi. I’ve been told this is normal. 
The only thing that is odd, if my prop is turned at all, I might loose prime.
So NOBODY touches my prop!
If not touched I can go months and all is good.
If prime is lose, I have to take off the oil filter and back prime the system.
Also when changing oil, I back prime.

That’s my story.

Kevin



On Jul 14, 2022, at 9:31 PM, Jerry Marstall <jerrylm1986@...> wrote:


Thx Corbin.  The Continental specs list normal oil pressure as 30-60.

Hey gang, what are some of your readings?


On Thu, Jul 14, 2022, 7:01 PM Corbin via groups.io <c_geiser=icloud.com@groups.io> wrote:
Jerry,

That is my typical oil pressure when I am hot in the summer.  I am no A&P but 25 psi is still in the green for a O-200A, I believe.  I remember two summers ago, the O-200 forums were telling me that if my oil psi was in line with my rpm then all was well if still in the green.  Example, 2400 rpm could yield 24 psi at these hotter summer temps.  Of course, the weight of oil used can make a difference as well.  Are you running 50W or 100W?

Now that I have more price digital engine instruments I am hoping for more accurate measurements.  But too hot to fly for me these days.

Again, I am no A&P so please don’t take my info to heart all on its own.

Corbin


On Jul 14, 2022, at 5:54 PM, Jerry Marstall <jerrylm1986@...> wrote:

That’s my problem – On initial start oil pressure is 40.  After oil temp approaches 140-180, the oil pressure works its way down to 25-30 and remains there.   At Keith’s Spring fling I brought up this problem and the consensus was it is either the gauge or the sensor.  I swapped in new ones and no improvement.  Sam pointed me to a source (see extract below) with a proposed solution that I would obviously like to avoid.  Before I leap into the money pit, does anyone have suggestions that I should pursue first?
Oil Pressure Drop at Operating Temperature
I have a J3 with a C-85 built up with the O-200 Crank, Rods, Pistons, and cylinders.The engine has roughly 700 smoh and recently it started losing oil pressure as the oil temp reaches 140 F.As the oil temp rises the oil pressure falls until the oil pressure reaches about 12 PSI.My mechanic has tried everything he can think of. I am sorry to say that we did a bottom end on the engine (turned the crank and replaced the main bearings) only to find that the problem still exists.I read the section of your QA where someone had a cracked lifter body that caused a loss of oil pressure.Do you think that this could be my problem as well?Any help would be greatly appreciated as the downtime and maintenance bills are getting pretty extensive at this point.
About half the questions I answer regard low oil pressure on these little Continentals.
If the crank has been machined and matched to new rod and main bearings, we can reasonably take that part of the system out of consideration.This narrows it down to other parts of the pressure system.
A cracked tappet body might contribute to low oil pressure, but this would not be a subtle problem to discover.A typical problem is that the little cup which fits into the tappet body pops out and gets wedged between the pushrod and the tappet body.Usually, the pushrod bends and the engine runs poorly, among other problems.
I did have an operator report that the bores for the tappet bodies in the crankcase were worn and ovaled which led to low overall oil pressure.I have not confirmed that this can result in low oil pressure since the bores are not pressure fed.But, the report came from a reputable source.
If I were to wager, I'd bet that the problem is more likely with the oil pump in the accessory case.This is a chronic weak spot with the little Continentals.If the tolerances are marginal, the engine will produce acceptable pressure, but as the engine warms, the tolerances open up and the pump loses pressure.I just fixed up a friend's C-85-12 installed on a Cessna 140 which exhibited exactly the same problem.We installed a new manufacture accessory case and the problem was fixed.
The oil pump consists of two gears, a cover plate and the oil pump cavity which is cast integral into the accessory case.If the oil pump bores become worn or grooved, the edge clearance between the oil pump gears and the becomes too great and the pump can't maintain pressure.The shaft holes for the pump gears also wear and pressure is lost.Finally, the cover plate can warp and oil will leak past causing low oil pressure.
So, my feeling is that the problem is probably with the oil pump in the accessory case.It is a fairly involved job to remove the accessory case, but no way around it.
You don't mention if you have a -8 or -12 engine, but here is the summary. The -8 case is magnesium and requires very special techniques to repair. Pretty much, the only place to get this work done is Drake Air, Tulsa, OK. www.DrakeAir.com, 918-445-3545.If the engine is a -12, then new cases are available for pretty reasonable cost (for airplane parts) from Mattituck, Edgecumbe G&N and others.My friend's case cost about $750 and another $150 for other parts along with about four hours of our free labor.
If you take a read through the Engine archive at the Fly Baby website, you will find that the accessory case is probably the number one problem with all Continentals.
 
 


--

Corbin 
N121CG


Kevin Boddicker
 

Bruce,
Any rpm at start will yield 40 psi. Sometimes it takes a while to move the needle.
Usually during cold weather. 
The only time I see below 40 PSI is during taxi after landing.
I don’t pay much to oil pressure during landing. Imagine that.
I have checked the op gauge with air pressure. It matches the pressure set on the compressor.

Kevin


On Jul 15, 2022, at 1:31 PM, Bruce Crain <jcrain2@...> wrote:

Kevin will turning up the rpms at start up bring the oil pressure up?  I have to do that if I haven’t flown in a month or so.
Bruce


On Jul 15, 2022, at 1:00 PM, Paul Fisher <rv7a.n18pf@...> wrote:


You made me look!

Sorry for the delayed response Jerry, I have an old analog oil pressure gauge so I don't pay attention to the absolute value - I just verify the needle is in the correct position.  I had to come to the airport to see what value that position equated to!

My green arc is indeed 30-60 psi, and I tend to run about 30-35 most of the time.  As Kevin said, when it's hot and at idle it will drop to ~20, but will increase with an increase in RPM.

Having said all that I have never tried to calibrate the guage.  So I have no idea how accurate those numbers are.  I don't worry about oil pressure.  But then again I don't live in the mountains!  Where I fly there is usually a corn field within 15 to 20 feet of me!!

Good luck!

Paul 

On Thu, Jul 14, 2022, 21:31 Jerry Marstall <jerrylm1986@...> wrote:
Thx Corbin.  The Continental specs list normal oil pressure as 30-60.

Hey gang, what are some of your readings?


On Thu, Jul 14, 2022, 7:01 PM Corbin via groups.io <c_geiser=icloud.com@groups.io> wrote:
Jerry,

That is my typical oil pressure when I am hot in the summer.  I am no A&P but 25 psi is still in the green for a O-200A, I believe.  I remember two summers ago, the O-200 forums were telling me that if my oil psi was in line with my rpm then all was well if still in the green.  Example, 2400 rpm could yield 24 psi at these hotter summer temps.  Of course, the weight of oil used can make a difference as well.  Are you running 50W or 100W?

Now that I have more price digital engine instruments I am hoping for more accurate measurements.  But too hot to fly for me these days.

Again, I am no A&P so please don’t take my info to heart all on its own.

Corbin


On Jul 14, 2022, at 5:54 PM, Jerry Marstall <jerrylm1986@...> wrote:

That’s my problem – On initial start oil pressure is 40.  After oil temp approaches 140-180, the oil pressure works its way down to 25-30 and remains there.   At Keith’s Spring fling I brought up this problem and the consensus was it is either the gauge or the sensor.  I swapped in new ones and no improvement.  Sam pointed me to a source (see extract below) with a proposed solution that I would obviously like to avoid.  Before I leap into the money pit, does anyone have suggestions that I should pursue first?
Oil Pressure Drop at Operating Temperature
I have a J3 with a C-85 built up with the O-200 Crank, Rods, Pistons, and cylinders.The engine has roughly 700 smoh and recently it started losing oil pressure as the oil temp reaches 140 F.As the oil temp rises the oil pressure falls until the oil pressure reaches about 12 PSI.My mechanic has tried everything he can think of. I am sorry to say that we did a bottom end on the engine (turned the crank and replaced the main bearings) only to find that the problem still exists.I read the section of your QA where someone had a cracked lifter body that caused a loss of oil pressure.Do you think that this could be my problem as well?Any help would be greatly appreciated as the downtime and maintenance bills are getting pretty extensive at this point.
About half the questions I answer regard low oil pressure on these little Continentals.
If the crank has been machined and matched to new rod and main bearings, we can reasonably take that part of the system out of consideration.This narrows it down to other parts of the pressure system.
A cracked tappet body might contribute to low oil pressure, but this would not be a subtle problem to discover.A typical problem is that the little cup which fits into the tappet body pops out and gets wedged between the pushrod and the tappet body.Usually, the pushrod bends and the engine runs poorly, among other problems.
I did have an operator report that the bores for the tappet bodies in the crankcase were worn and ovaled which led to low overall oil pressure.I have not confirmed that this can result in low oil pressure since the bores are not pressure fed.But, the report came from a reputable source.
If I were to wager, I'd bet that the problem is more likely with the oil pump in the accessory case.This is a chronic weak spot with the little Continentals.If the tolerances are marginal, the engine will produce acceptable pressure, but as the engine warms, the tolerances open up and the pump loses pressure.I just fixed up a friend's C-85-12 installed on a Cessna 140 which exhibited exactly the same problem.We installed a new manufacture accessory case and the problem was fixed.
The oil pump consists of two gears, a cover plate and the oil pump cavity which is cast integral into the accessory case.If the oil pump bores become worn or grooved, the edge clearance between the oil pump gears and the becomes too great and the pump can't maintain pressure.The shaft holes for the pump gears also wear and pressure is lost.Finally, the cover plate can warp and oil will leak past causing low oil pressure.
So, my feeling is that the problem is probably with the oil pump in the accessory case.It is a fairly involved job to remove the accessory case, but no way around it.
You don't mention if you have a -8 or -12 engine, but here is the summary. The -8 case is magnesium and requires very special techniques to repair. Pretty much, the only place to get this work done is Drake Air, Tulsa, OK. www.DrakeAir.com, 918-445-3545.If the engine is a -12, then new cases are available for pretty reasonable cost (for airplane parts) from Mattituck, Edgecumbe G&N and others.My friend's case cost about $750 and another $150 for other parts along with about four hours of our free labor.
If you take a read through the Engine archive at the Fly Baby website, you will find that the accessory case is probably the number one problem with all Continentals.
 
 


--

Corbin 
N121CG


Jay Scheevel
 

Hi Kevin,

 

I have a very small lady inside my EFIS that tells me over the intercom if there is an oil pressure problem. She lets me do the flying (most of the time), but she is very insistent when there is something amiss. 😉

 

Cheers,

Jay

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Kevin Boddicker
Sent: Friday, July 15, 2022 5:02 PM
To: main@q-list.groups.io
Subject: Re: [Q-List] Oil pressure dropping at operating temperature.

 

Bruce,

Any rpm at start will yield 40 psi. Sometimes it takes a while to move the needle.

Usually during cold weather. 

The only time I see below 40 PSI is during taxi after landing.

I don’t pay much to oil pressure during landing. Imagine that.

I have checked the op gauge with air pressure. It matches the pressure set on the compressor.

 

Kevin

 



On Jul 15, 2022, at 1:31 PM, Bruce Crain <jcrain2@...> wrote:

Kevin will turning up the rpms at start up bring the oil pressure up?  I have to do that if I haven’t flown in a month or so.

Bruce



On Jul 15, 2022, at 1:00 PM, Paul Fisher <rv7a.n18pf@...> wrote:



You made me look!

 

Sorry for the delayed response Jerry, I have an old analog oil pressure gauge so I don't pay attention to the absolute value - I just verify the needle is in the correct position.  I had to come to the airport to see what value that position equated to!

 

My green arc is indeed 30-60 psi, and I tend to run about 30-35 most of the time.  As Kevin said, when it's hot and at idle it will drop to ~20, but will increase with an increase in RPM.

 

Having said all that I have never tried to calibrate the guage.  So I have no idea how accurate those numbers are.  I don't worry about oil pressure.  But then again I don't live in the mountains!  Where I fly there is usually a corn field within 15 to 20 feet of me!!

 

Good luck!

 

Paul 

On Thu, Jul 14, 2022, 21:31 Jerry Marstall <jerrylm1986@...> wrote:

Thx Corbin.  The Continental specs list normal oil pressure as 30-60.

 

Hey gang, what are some of your readings?

 

 

On Thu, Jul 14, 2022, 7:01 PM Corbin via groups.io <c_geiser=icloud.com@groups.io> wrote:

Jerry,

 

That is my typical oil pressure when I am hot in the summer.  I am no A&P but 25 psi is still in the green for a O-200A, I believe.  I remember two summers ago, the O-200 forums were telling me that if my oil psi was in line with my rpm then all was well if still in the green.  Example, 2400 rpm could yield 24 psi at these hotter summer temps.  Of course, the weight of oil used can make a difference as well.  Are you running 50W or 100W?

 

Now that I have more price digital engine instruments I am hoping for more accurate measurements.  But too hot to fly for me these days.

 

Again, I am no A&P so please don’t take my info to heart all on its own.

 

Corbin

 



On Jul 14, 2022, at 5:54 PM, Jerry Marstall <jerrylm1986@...> wrote:

 

That’s my problem – On initial start oil pressure is 40.  After oil temp approaches 140-180, the oil pressure works its way down to 25-30 and remains there.   At Keith’s Spring fling I brought up this problem and the consensus was it is either the gauge or the sensor.  I swapped in new ones and no improvement.  Sam pointed me to a source (see extract below) with a proposed solution that I would obviously like to avoid.  Before I leap into the money pit, does anyone have suggestions that I should pursue first?

Oil Pressure Drop at Operating Temperature

I have a J3 with a C-85 built up with the O-200 Crank, Rods, Pistons, and cylinders.The engine has roughly 700 smoh and recently it started losing oil pressure as the oil temp reaches 140 F.As the oil temp rises the oil pressure falls until the oil pressure reaches about 12 PSI.My mechanic has tried everything he can think of. I am sorry to say that we did a bottom end on the engine (turned the crank and replaced the main bearings) only to find that the problem still exists.I read the section of your QA where someone had a cracked lifter body that caused a loss of oil pressure.Do you think that this could be my problem as well?Any help would be greatly appreciated as the downtime and maintenance bills are getting pretty extensive at this point.

About half the questions I answer regard low oil pressure on these little Continentals.

If the crank has been machined and matched to new rod and main bearings, we can reasonably take that part of the system out of consideration.This narrows it down to other parts of the pressure system.

A cracked tappet body might contribute to low oil pressure, but this would not be a subtle problem to discover.A typical problem is that the little cup which fits into the tappet body pops out and gets wedged between the pushrod and the tappet body.Usually, the pushrod bends and the engine runs poorly, among other problems.

I did have an operator report that the bores for the tappet bodies in the crankcase were worn and ovaled which led to low overall oil pressure.I have not confirmed that this can result in low oil pressure since the bores are not pressure fed.But, the report came from a reputable source.

If I were to wager, I'd bet that the problem is more likely with the oil pump in the accessory case.This is a chronic weak spot with the little Continentals.If the tolerances are marginal, the engine will produce acceptable pressure, but as the engine warms, the tolerances open up and the pump loses pressure.I just fixed up a friend's C-85-12 installed on a Cessna 140 which exhibited exactly the same problem.We installed a new manufacture accessory case and the problem was fixed.

The oil pump consists of two gears, a cover plate and the oil pump cavity which is cast integral into the accessory case.If the oil pump bores become worn or grooved, the edge clearance between the oil pump gears and the becomes too great and the pump can't maintain pressure.The shaft holes for the pump gears also wear and pressure is lost.Finally, the cover plate can warp and oil will leak past causing low oil pressure.

So, my feeling is that the problem is probably with the oil pump in the accessory case.It is a fairly involved job to remove the accessory case, but no way around it.

You don't mention if you have a -8 or -12 engine, but here is the summary. The -8 case is magnesium and requires very special techniques to repair. Pretty much, the only place to get this work done is Drake Air, Tulsa, OK. www.DrakeAir.com, 918-445-3545.If the engine is a -12, then new cases are available for pretty reasonable cost (for airplane parts) from Mattituck, Edgecumbe G&N and others.My friend's case cost about $750 and another $150 for other parts along with about four hours of our free labor.

If you take a read through the Engine archive at the Fly Baby website, you will find that the accessory case is probably the number one problem with all Continentals.

 

 

 


--

Corbin 
N121CG


Jerry Marstall
 

Thx Paul.  Mine is similar to yours, except about 5psi less.  I'm thinking mine never has been 40.  Maybe I just woke up.  Now that I am awake I would feel more comfortable if it read 30+ at cruise. Jm


On Fri, Jul 15, 2022, 7:01 PM Kevin Boddicker <trumanst@...> wrote:
Bruce,
Any rpm at start will yield 40 psi. Sometimes it takes a while to move the needle.
Usually during cold weather. 
The only time I see below 40 PSI is during taxi after landing.
I don’t pay much to oil pressure during landing. Imagine that.
I have checked the op gauge with air pressure. It matches the pressure set on the compressor.

Kevin


On Jul 15, 2022, at 1:31 PM, Bruce Crain <jcrain2@...> wrote:

Kevin will turning up the rpms at start up bring the oil pressure up?  I have to do that if I haven’t flown in a month or so.
Bruce


On Jul 15, 2022, at 1:00 PM, Paul Fisher <rv7a.n18pf@...> wrote:


You made me look!

Sorry for the delayed response Jerry, I have an old analog oil pressure gauge so I don't pay attention to the absolute value - I just verify the needle is in the correct position.  I had to come to the airport to see what value that position equated to!

My green arc is indeed 30-60 psi, and I tend to run about 30-35 most of the time.  As Kevin said, when it's hot and at idle it will drop to ~20, but will increase with an increase in RPM.

Having said all that I have never tried to calibrate the guage.  So I have no idea how accurate those numbers are.  I don't worry about oil pressure.  But then again I don't live in the mountains!  Where I fly there is usually a corn field within 15 to 20 feet of me!!

Good luck!

Paul 

On Thu, Jul 14, 2022, 21:31 Jerry Marstall <jerrylm1986@...> wrote:
Thx Corbin.  The Continental specs list normal oil pressure as 30-60.

Hey gang, what are some of your readings?


On Thu, Jul 14, 2022, 7:01 PM Corbin via groups.io <c_geiser=icloud.com@groups.io> wrote:
Jerry,

That is my typical oil pressure when I am hot in the summer.  I am no A&P but 25 psi is still in the green for a O-200A, I believe.  I remember two summers ago, the O-200 forums were telling me that if my oil psi was in line with my rpm then all was well if still in the green.  Example, 2400 rpm could yield 24 psi at these hotter summer temps.  Of course, the weight of oil used can make a difference as well.  Are you running 50W or 100W?

Now that I have more price digital engine instruments I am hoping for more accurate measurements.  But too hot to fly for me these days.

Again, I am no A&P so please don’t take my info to heart all on its own.

Corbin


On Jul 14, 2022, at 5:54 PM, Jerry Marstall <jerrylm1986@...> wrote:

That’s my problem – On initial start oil pressure is 40.  After oil temp approaches 140-180, the oil pressure works its way down to 25-30 and remains there.   At Keith’s Spring fling I brought up this problem and the consensus was it is either the gauge or the sensor.  I swapped in new ones and no improvement.  Sam pointed me to a source (see extract below) with a proposed solution that I would obviously like to avoid.  Before I leap into the money pit, does anyone have suggestions that I should pursue first?
Oil Pressure Drop at Operating Temperature
I have a J3 with a C-85 built up with the O-200 Crank, Rods, Pistons, and cylinders.The engine has roughly 700 smoh and recently it started losing oil pressure as the oil temp reaches 140 F.As the oil temp rises the oil pressure falls until the oil pressure reaches about 12 PSI.My mechanic has tried everything he can think of. I am sorry to say that we did a bottom end on the engine (turned the crank and replaced the main bearings) only to find that the problem still exists.I read the section of your QA where someone had a cracked lifter body that caused a loss of oil pressure.Do you think that this could be my problem as well?Any help would be greatly appreciated as the downtime and maintenance bills are getting pretty extensive at this point.
About half the questions I answer regard low oil pressure on these little Continentals.
If the crank has been machined and matched to new rod and main bearings, we can reasonably take that part of the system out of consideration.This narrows it down to other parts of the pressure system.
A cracked tappet body might contribute to low oil pressure, but this would not be a subtle problem to discover.A typical problem is that the little cup which fits into the tappet body pops out and gets wedged between the pushrod and the tappet body.Usually, the pushrod bends and the engine runs poorly, among other problems.
I did have an operator report that the bores for the tappet bodies in the crankcase were worn and ovaled which led to low overall oil pressure.I have not confirmed that this can result in low oil pressure since the bores are not pressure fed.But, the report came from a reputable source.
If I were to wager, I'd bet that the problem is more likely with the oil pump in the accessory case.This is a chronic weak spot with the little Continentals.If the tolerances are marginal, the engine will produce acceptable pressure, but as the engine warms, the tolerances open up and the pump loses pressure.I just fixed up a friend's C-85-12 installed on a Cessna 140 which exhibited exactly the same problem.We installed a new manufacture accessory case and the problem was fixed.
The oil pump consists of two gears, a cover plate and the oil pump cavity which is cast integral into the accessory case.If the oil pump bores become worn or grooved, the edge clearance between the oil pump gears and the becomes too great and the pump can't maintain pressure.The shaft holes for the pump gears also wear and pressure is lost.Finally, the cover plate can warp and oil will leak past causing low oil pressure.
So, my feeling is that the problem is probably with the oil pump in the accessory case.It is a fairly involved job to remove the accessory case, but no way around it.
You don't mention if you have a -8 or -12 engine, but here is the summary. The -8 case is magnesium and requires very special techniques to repair. Pretty much, the only place to get this work done is Drake Air, Tulsa, OK. www.DrakeAir.com, 918-445-3545.If the engine is a -12, then new cases are available for pretty reasonable cost (for airplane parts) from Mattituck, Edgecumbe G&N and others.My friend's case cost about $750 and another $150 for other parts along with about four hours of our free labor.
If you take a read through the Engine archive at the Fly Baby website, you will find that the accessory case is probably the number one problem with all Continentals.
 
 


--

Corbin 
N121CG


Mike Dwyer
 

Back in 1985 when I bought the rebuilt 0-200A for $3500 I had 30 PSI at 210F with W100 = 50 weight oil.  At idle it would only drop to 25 or so.  36 years later at 150F I'd see 30 at best and 10 at idle.  Over 150F the pressure would drop a lot.  I often taxied back with 10 PSI and didn't like it.  Did new bearings and a crank and case due to failing magnaflux and made no difference in oil pressure.  I was looking at buying a new AL accessory case but they are $2000 now.  I really think it was a worn oil pump (part of the accessory case) that caused the low oil pressure.  The oil pressure was always 40 PSI after the first start with cold oil.
Mike Dwyer

Q200 Website: http://goo.gl/V8IrJF


On Thu, Jul 14, 2022 at 10:31 PM Jerry Marstall <jerrylm1986@...> wrote:
Thx Corbin.  The Continental specs list normal oil pressure as 30-60.

Hey gang, what are some of your readings?


On Thu, Jul 14, 2022, 7:01 PM Corbin via groups.io <c_geiser=icloud.com@groups.io> wrote:
Jerry,

That is my typical oil pressure when I am hot in the summer.  I am no A&P but 25 psi is still in the green for a O-200A, I believe.  I remember two summers ago, the O-200 forums were telling me that if my oil psi was in line with my rpm then all was well if still in the green.  Example, 2400 rpm could yield 24 psi at these hotter summer temps.  Of course, the weight of oil used can make a difference as well.  Are you running 50W or 100W?

Now that I have more price digital engine instruments I am hoping for more accurate measurements.  But too hot to fly for me these days.

Again, I am no A&P so please don’t take my info to heart all on its own.

Corbin


On Jul 14, 2022, at 5:54 PM, Jerry Marstall <jerrylm1986@...> wrote:

That’s my problem – On initial start oil pressure is 40.  After oil temp approaches 140-180, the oil pressure works its way down to 25-30 and remains there.   At Keith’s Spring fling I brought up this problem and the consensus was it is either the gauge or the sensor.  I swapped in new ones and no improvement.  Sam pointed me to a source (see extract below) with a proposed solution that I would obviously like to avoid.  Before I leap into the money pit, does anyone have suggestions that I should pursue first?
Oil Pressure Drop at Operating Temperature
I have a J3 with a C-85 built up with the O-200 Crank, Rods, Pistons, and cylinders.The engine has roughly 700 smoh and recently it started losing oil pressure as the oil temp reaches 140 F.As the oil temp rises the oil pressure falls until the oil pressure reaches about 12 PSI.My mechanic has tried everything he can think of. I am sorry to say that we did a bottom end on the engine (turned the crank and replaced the main bearings) only to find that the problem still exists.I read the section of your QA where someone had a cracked lifter body that caused a loss of oil pressure.Do you think that this could be my problem as well?Any help would be greatly appreciated as the downtime and maintenance bills are getting pretty extensive at this point.
About half the questions I answer regard low oil pressure on these little Continentals.
If the crank has been machined and matched to new rod and main bearings, we can reasonably take that part of the system out of consideration.This narrows it down to other parts of the pressure system.
A cracked tappet body might contribute to low oil pressure, but this would not be a subtle problem to discover.A typical problem is that the little cup which fits into the tappet body pops out and gets wedged between the pushrod and the tappet body.Usually, the pushrod bends and the engine runs poorly, among other problems.
I did have an operator report that the bores for the tappet bodies in the crankcase were worn and ovaled which led to low overall oil pressure.I have not confirmed that this can result in low oil pressure since the bores are not pressure fed.But, the report came from a reputable source.
If I were to wager, I'd bet that the problem is more likely with the oil pump in the accessory case.This is a chronic weak spot with the little Continentals.If the tolerances are marginal, the engine will produce acceptable pressure, but as the engine warms, the tolerances open up and the pump loses pressure.I just fixed up a friend's C-85-12 installed on a Cessna 140 which exhibited exactly the same problem.We installed a new manufacture accessory case and the problem was fixed.
The oil pump consists of two gears, a cover plate and the oil pump cavity which is cast integral into the accessory case.If the oil pump bores become worn or grooved, the edge clearance between the oil pump gears and the becomes too great and the pump can't maintain pressure.The shaft holes for the pump gears also wear and pressure is lost.Finally, the cover plate can warp and oil will leak past causing low oil pressure.
So, my feeling is that the problem is probably with the oil pump in the accessory case.It is a fairly involved job to remove the accessory case, but no way around it.
You don't mention if you have a -8 or -12 engine, but here is the summary. The -8 case is magnesium and requires very special techniques to repair. Pretty much, the only place to get this work done is Drake Air, Tulsa, OK. www.DrakeAir.com, 918-445-3545.If the engine is a -12, then new cases are available for pretty reasonable cost (for airplane parts) from Mattituck, Edgecumbe G&N and others.My friend's case cost about $750 and another $150 for other parts along with about four hours of our free labor.
If you take a read through the Engine archive at the Fly Baby website, you will find that the accessory case is probably the number one problem with all Continentals.
 
 


--

Corbin 
N121CG


Jerry Marstall
 

Thank you Mike. VERY helpful. Jm


On Fri, Jul 15, 2022, 8:36 PM Mike Dwyer <q200pilot@...> wrote:
Back in 1985 when I bought the rebuilt 0-200A for $3500 I had 30 PSI at 210F with W100 = 50 weight oil.  At idle it would only drop to 25 or so.  36 years later at 150F I'd see 30 at best and 10 at idle.  Over 150F the pressure would drop a lot.  I often taxied back with 10 PSI and didn't like it.  Did new bearings and a crank and case due to failing magnaflux and made no difference in oil pressure.  I was looking at buying a new AL accessory case but they are $2000 now.  I really think it was a worn oil pump (part of the accessory case) that caused the low oil pressure.  The oil pressure was always 40 PSI after the first start with cold oil.
Mike Dwyer

Q200 Website: http://goo.gl/V8IrJF


On Thu, Jul 14, 2022 at 10:31 PM Jerry Marstall <jerrylm1986@...> wrote:
Thx Corbin.  The Continental specs list normal oil pressure as 30-60.

Hey gang, what are some of your readings?


On Thu, Jul 14, 2022, 7:01 PM Corbin via groups.io <c_geiser=icloud.com@groups.io> wrote:
Jerry,

That is my typical oil pressure when I am hot in the summer.  I am no A&P but 25 psi is still in the green for a O-200A, I believe.  I remember two summers ago, the O-200 forums were telling me that if my oil psi was in line with my rpm then all was well if still in the green.  Example, 2400 rpm could yield 24 psi at these hotter summer temps.  Of course, the weight of oil used can make a difference as well.  Are you running 50W or 100W?

Now that I have more price digital engine instruments I am hoping for more accurate measurements.  But too hot to fly for me these days.

Again, I am no A&P so please don’t take my info to heart all on its own.

Corbin


On Jul 14, 2022, at 5:54 PM, Jerry Marstall <jerrylm1986@...> wrote:

That’s my problem – On initial start oil pressure is 40.  After oil temp approaches 140-180, the oil pressure works its way down to 25-30 and remains there.   At Keith’s Spring fling I brought up this problem and the consensus was it is either the gauge or the sensor.  I swapped in new ones and no improvement.  Sam pointed me to a source (see extract below) with a proposed solution that I would obviously like to avoid.  Before I leap into the money pit, does anyone have suggestions that I should pursue first?
Oil Pressure Drop at Operating Temperature
I have a J3 with a C-85 built up with the O-200 Crank, Rods, Pistons, and cylinders.The engine has roughly 700 smoh and recently it started losing oil pressure as the oil temp reaches 140 F.As the oil temp rises the oil pressure falls until the oil pressure reaches about 12 PSI.My mechanic has tried everything he can think of. I am sorry to say that we did a bottom end on the engine (turned the crank and replaced the main bearings) only to find that the problem still exists.I read the section of your QA where someone had a cracked lifter body that caused a loss of oil pressure.Do you think that this could be my problem as well?Any help would be greatly appreciated as the downtime and maintenance bills are getting pretty extensive at this point.
About half the questions I answer regard low oil pressure on these little Continentals.
If the crank has been machined and matched to new rod and main bearings, we can reasonably take that part of the system out of consideration.This narrows it down to other parts of the pressure system.
A cracked tappet body might contribute to low oil pressure, but this would not be a subtle problem to discover.A typical problem is that the little cup which fits into the tappet body pops out and gets wedged between the pushrod and the tappet body.Usually, the pushrod bends and the engine runs poorly, among other problems.
I did have an operator report that the bores for the tappet bodies in the crankcase were worn and ovaled which led to low overall oil pressure.I have not confirmed that this can result in low oil pressure since the bores are not pressure fed.But, the report came from a reputable source.
If I were to wager, I'd bet that the problem is more likely with the oil pump in the accessory case.This is a chronic weak spot with the little Continentals.If the tolerances are marginal, the engine will produce acceptable pressure, but as the engine warms, the tolerances open up and the pump loses pressure.I just fixed up a friend's C-85-12 installed on a Cessna 140 which exhibited exactly the same problem.We installed a new manufacture accessory case and the problem was fixed.
The oil pump consists of two gears, a cover plate and the oil pump cavity which is cast integral into the accessory case.If the oil pump bores become worn or grooved, the edge clearance between the oil pump gears and the becomes too great and the pump can't maintain pressure.The shaft holes for the pump gears also wear and pressure is lost.Finally, the cover plate can warp and oil will leak past causing low oil pressure.
So, my feeling is that the problem is probably with the oil pump in the accessory case.It is a fairly involved job to remove the accessory case, but no way around it.
You don't mention if you have a -8 or -12 engine, but here is the summary. The -8 case is magnesium and requires very special techniques to repair. Pretty much, the only place to get this work done is Drake Air, Tulsa, OK. www.DrakeAir.com, 918-445-3545.If the engine is a -12, then new cases are available for pretty reasonable cost (for airplane parts) from Mattituck, Edgecumbe G&N and others.My friend's case cost about $750 and another $150 for other parts along with about four hours of our free labor.
If you take a read through the Engine archive at the Fly Baby website, you will find that the accessory case is probably the number one problem with all Continentals.
 
 


--

Corbin 
N121CG