[f-AA] Low Oil Pressure on C85-12

[Sam Burke]

I have a new bebuilt C85 engine and during the break in flight I experienced 22 pounds of oil pressure at 210 deg F.  

The Aeronca L16A manual shows 25 to 35 psi as normal during cruise.  When I dissembled the oil pressure regulator valve it had a short spring.  An A and P friend had a spring from a standard C85 which was about 0.75 inch longer which we installed and tested with better results (ie. 34 psi at 175 deg F) and 22 psi at 800 rpm idle. I wish to order an Aeronca PN 21352 spring but am unable to find anyone with one, any suggestions would be appreciated. I want to see if the spring with the 21352 part number is the same or different than what I had in my engine on delivery from the rebuild shop.  Anyone with experience here?

Regards,

Sam Burke N6404C  1947 L16A  C85-12  7BCM-296  USAF 47-1076

[j...@joea.com]

Something else is wrong here.

A correctly overhauled C-85 should not have oil pressure this low, no matter which spring is in the relief valve.

Joe A

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[Sam Burke]

Hi Joe,  What do you make of the fact that the longer (possibly the correct) spring seems to have corrected the problem?  

[Stephen Briggs]

Joe is correct, the spring length is key to getting the correct oil pressure.  If the spring is stiill short it is acceptable to place a washer or two in the bottom of the hole where the spring rests.  I had a similar issue with a 65 and the problem was nicely resolved with a washer.  The spring tension is necessary in setting the oil pressure.

Steve

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From: samb...@verizon.net
Date: Wed, 22 Aug 2012 22:12:41 -0700
To: aer...@westmont.edu
CC: samb...@verizon.net; dick.f...@mac.com; flyf...@gmail.com
Subject: [f-AA] Low Oil Pressure on C85-12

Hi Joe,  What do you make of the fact that the longer (possibly the correct) spring seems to have corrected the problem?  

Regards,

Sam Burke N6404C  1947 L16A  C85-12  7BCM-296  USAF 47-1076

_______________________________________________ Aeronca mailing list Aer...@westmont.edu http://mail.westmont.edu/mailman/listinfo/aeronca

[Cy Galley]

I believe that all engine parts are Continental not Aeronca and should be ordered from Continental parts sources with Continental numbers.

 

Cy Galley - Chair, AirVenture Emergency Aircraft Repair

A service project of EAA Chapter 75 since 1963

www.eaa75.com

 

 

 

From: aeronca...@westmont.edu [mailto:aeronca...@westmont.edu] On Behalf Of Sam Burke
Sent: Wednesday, August 22, 2012 11:06 PM
To: aer...@westmont.edu
Cc: Pat Burke; Dick Fischer; Lane Tufts; Don Noonan
Subject: [f-AA] Low Oil Pressure on C85-12

 

I have a new bebuilt C85 engine and during the break in flight I experienced 22 pounds of oil pressure at 210 deg F.  

[Sam Burke]

Steve, 

Yes the longer spring PN 21352 has increased my cruise oil pressure from 22 to 35 psi with the idle rpm changing from 15 to 22 psi.  The short spring that I found in my oil pressure relief assembly is PN 637083, it does not show up in the Continental "C" Parts Catalog, not sure about it's purpose. 

[Sam Burke]

Cy, 

I found one at Fresno Air Parts for $5.00, thanks. 

[Roger Anderson]

I'm confused about this spring thing.  Are we talking about the spring in the pressure relief valve...or another spring somewhere else.  I understood that the pressure relief valve spring can in no way increase low end pressure, only regulate the high end pressure.  In other words, whatever the pressure shows after the engine is warmed up to normal operating temps, nothing except a rebuild is going to change that.   ?????

---

From: "Cy Galley" <cga...@mchsi.com>
To: aer...@westmont.edu
Sent: Thursday, August 23, 2012 8:16:32 AM
Subject: Re: [f-AA] Low Oil Pressure on C85-12

[David Rude PE]

Based on what you said the longer spring did not solve the problem, to prove that it did you must take the oil press at the same oil temps and I don't think you did that.

A better question may be this; what was done to the oil pump at overhaul?

Was the cavity to gear clearance checked and correct as needed?

Was the plate checked?

Was the gear shaft to cover hole clearance checked and corrected as needed?

Where the gear teeth checked?

If the answer to these questions are no then that is likely the problem.

These are expensive corrections and therefore may have been avoided.

I suppose one might also ask what grade oil is in ?

Hope this helps, Dave

[Roger Anderson]

Same oil temps would be important for comparison.  My A65 drops about 2 lbs of pressure for about each 5 degrees of temp increase.....once the temps get up in the 150 degree range or so. 

---

From: "David Rude PE" <dr...@us.ibm.com>
To: aer...@westmont.edu
Sent: Thursday, August 23, 2012 9:04:23 AM

Subject: Re: [f-AA] Low Oil Pressure on C85-12

Based on what you said the longer spring did not solve the problem, to prove that it did you must take the oil press at the same oil temps and I don't think you did that.

[j...@joea.com]

Agree with Dave's comments below.

My C-145 is essentially a C-85 engine with two additional cylinders. When I start the engine it goes up to about 39 psi oil pressure. Stays there until the oil gets warm then drops down to about 37 psi and never gets lower. Never...

My old Chief had a C-85 on it and had about the same readings and behavior. Yours if fluctuating a good 15 psi from cold startup to hot and running speed to idle.

If you are very, very lucky your oil pressure relief valve has something stuck in it and that's where the pressure is escaping. If its not there, then its inside the engine somewhere and truthfully if it were my engine/airplane. As it sounds like you have pulled the spring out of the oil pressure relief valve several times already, am guessing that this is not the culprit.

Personally I would be taking it back to the mechanic and having them tear it down and do it right this time. Something is not right with your engines oil pressure system and I would not accept the engine "as is" until its fixed.

Joe A

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To:                             aer...@westmont.edu

From:                         David Rude PE <dr...@us.ibm.com>

Date sent:                  Thu, 23 Aug 2012 10:04:23 -0400

Subject:                     Re: [f-AA] Low Oil Pressure on C85-12

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[j...@joea.com]

Roger,

Correct. This spring only controls pressure that is excessive and dumped when it gets to be too high. There is no other spring in the oil system that can change the readings.

Unless the wrong spring was installed and the one in the engine is way low in tension, there is no way that its going to allow low oil pressure readings like this. Still its worth checking to make sure before tearing the engine apart.

Joe A

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Date sent:                   Thu, 23 Aug 2012 13:46:13 +0000 (UTC)

From:                         Roger Anderson <11...@comcast.net>

To:                             aer...@westmont.edu

Subject:                     Re: [f-AA] Low Oil Pressure on C85-12

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[j...@joea.com]

Sam,

Put the correct spring that Continental recommends in the pressure relief valve and see what readings you have. No one should have to "mix and match" relief springs to come up with what they feel is a proper oil pressure reading. An engine that has been overhauled "to factory specs" will have excellent oil pressure immediately upon startup.

To tell the truth, my first question would be "where did the spring that was in the engine come from in the first place?"  Is this the spring that was in the engine before it was overhauled? If not then the spring in the engine was replaced by the mechanic and I would ask why. Then ask where he got the spring from and the paperwork for the spring. If there is no paperwork, then the mechanic has a couple of very serious questions ahead of him.

As I have posted in other posts, your oil pressure should be stable and not vary as much as 15 psi. You say "corrected the problem" but personally I do not like the pressure varying 15 psi from idle to running speed and hot versus cold. This is not normal IMHO in small Continentals.

My engine varies about 3 psi from hot to cold and idle to cruise speed. The engine in my Chief was exactly the same way. Lets have others on the forum chime in on what their oil pressure does on their engines but am going to bet that most have a pretty stable oil pressure and that your readings is not the norm.

In its present status I would not fly the airplane.

Joe A

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From:                         Sam Burke <samb...@verizon.net>

Date sent:                  Wed, 22 Aug 2012 22:12:41 -0700

To:                             aer...@westmont.edu

Copies to:                  Pat Burke <samb...@verizon.net>, Dick Fischer <dick.f...@mac.com>,

                                  Lane Tufts <flyf...@gmail.com>

Subject:                     [f-AA]  Low Oil Pressure on C85-12

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[Cy Galley]

Read the Continental manual.  Some of the comments are much different than what the manual says on page 11 Table VII Operating Pressure Limits..  The minimum oil pressure at IDLE is 10 psi or over. Cruise is listed at 30 to 60 PSI.  If with hot oil your pressures are within these ranges , you are good to go according to the Continental Manual.

 

Use facts not opinions.

 

 

 

Cy Galley - Chair, AirVenture Emergency Aircraft Repair

A service project of EAA Chapter 75 since 1963

www.eaa75.com

 

 

From: aeronca...@westmont.edu [mailto:aeronca...@westmont.edu] On Behalf Of Sam Burke

Sent: Thursday, August 23, 2012 8:26 AM
To: aer...@westmont.edu
Cc: Pat Burke

Subject: [f-AA] Low Oil Pressure on C85-12

 

Steve, 

[David Rude PE]

Hi all,

Thinking a bit more about this I would also check the oil plunger condition as well as the seat in the crankcase that it fits in. If these leak you will loose the ability to regulate pressure also.

Dave

[cham...@gmail.com]

I think oil PSI numbers this variable are across a set of engines, with times varying from brand new to ready for overhaul.

I had a rebuilt A65 that varied from 10 to 60, at 50 hours SMOH. I looked at the book, and thought this was ok. Luckily my mechanic found the metal in the oil before it died in the air. We gave up on that engine. My "new" A65 is rock solid on oil PSI, and near 40 most of the time. If it's fairly "new", it should be low variability, and if it's getting near an overhaul, I would expect some variability.

I also would recommend a regular oil analysis. Find the metal this way before you can see it.

Regards, Bruce

[Cy Galley]

Spring 21352 is for the Dash 8. The listed number for a dash 12 is 631706

 

Cy

 

From: aeronca...@westmont.edu [mailto:aeronca...@westmont.edu] On Behalf Of Sam Burke

Sent: Thursday, August 23, 2012 8:26 AM
To: aer...@westmont.edu
Cc: Pat Burke

[CaptG...@aol.com]

Over time the oil pressure spring can take a set when manufacturered the wire temper is not quite right and after a time the heat can take some of the temper out of the spring. Those oil prerssure springs (the ones I have seen) are made of oil temp  wire and even over time 1/8 of a coil less in manufacturer and cause loss of tension and length. Some people take care of the loss of length with a washer. Springs are an art in themselves. I worked in a local Spring Factory in Michigan right out of school and was taught spring design by a master. Still have a spring design slide rule and manual after all these years. Engineering schools don't spend much time on spring design. We made valve springs for Ford and GM--a 1/4 turn difference can mean failure at 80000 miles or it will last forever. So much for spring rambling.

 

Doug

[John Rodkey]

I used to have oil pressure about 40 at cruise rpm when the oil temps were 170 or lower and down to about 30 when oil temps 180-200.  When the engine was idling, pressures were in the mid 20s when warm, and maybe 30 when cold.

Since the recent top overhaul (and replacement of piston rod bearings) pressures are about 35 at cruise when cold and down to 25 when hot.

They are low enough that it will be one of the items addressed while the engine is being looked at this Saturday and probably next week.

Two data points.  

John

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John (poobah) Rodkey - N9361E 11AC at Goleta

[j...@joea.com]

Dave,

Why check anything? Someone else is saying that "this is within limits" and should be left alone and flown!

Personally if I had just spent a lot of money and received an overhauled engine that acted like this, could care less about what the manual says. Something is not right inside that engine, but hey its not my rear end that will be sitting in the airplane when the engine gets tired of this.

Joe A

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To:                             aer...@westmont.edu

From:                         David Rude PE <dr...@us.ibm.com>

Date sent:                  Thu, 23 Aug 2012 11:57:08 -0400

Subject:                     Re: [f-AA] Low Oil Pressure on C85-12

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[Tom Pederson]

Did anyone question oil pressure gauge calibration?  Just wondering...missed it if it was mentioned.  

Tom

On Thu, Aug 23, 2012 at 9:34 AM, <CaptG...@aol.com> wrote:

Over time the oil pressure spring can take a set when manufacturered the wire temper is not quite right and after a time the heat can take some of the temper out of the spring. Those oil prerssure springs (the ones I have seen) are made of oil temp  wire and even over time 1/8 of a coil less in manufacturer and cause loss of tension and length. Some people take care of the loss of length with a washer. Springs are an art in themselves. I worked in a local Spring Factory in Michigan right out of school and was taught spring design by a master. Still have a spring design slide rule and manual after all these years. Engineering schools don't spend much time on spring design. We made valve springs for Ford and GM--a 1/4 turn difference can mean failure at 80000 miles or it will last forever. So much for spring rambling.

 

Doug

[David Rude PE]

Hi Joe,

I guess once I start thinking about it I just keep digging in further, once I start on some problem I don't let go until it seems thoroughly explored even whether it is needed or not!

That must be the engineer in me  coming out!

Dave

To:	aer...@westmont.edu

Subject:	Re: [f-AA] Low Oil Pressure on C85-12

[j...@joea.com]

Dave,

Totally agree and I would feel exactly the same. Evidently others do not feel that way and are content to accept an engine that "barely meets the specs" when for me a freshly overhauled engine should be on the upper end of the specs in this area.

Joe A

---

To:                             aer...@westmont.edu

From:                         David Rude PE <dr...@us.ibm.com>

Date sent:                  Thu, 23 Aug 2012 21:51:39 -0400

Subject:                     Re: [f-AA] Low Oil Pressure on C85-12

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[Sam Burke]

Carried out a test flight this morning with plans to travel from SMX (Santa Maria) to LPC (Lompoc) to check the oil pressure with the new spring in the oil pressure regulator. After 15 minutes the oil temperature had reached 195 deg F at 3000 ft with a 75 deg F Air Temp. At this point the oil pressure dropped from 30 psi (lower limit for cruise performance) to 24 psi.  I aborted the trip and turned back to SMX and landed.  I plan on meeting with a rep from the engine shop on Wednesday morning to discuss how to proceed. At this point I have 2.7 hours on my rebuilt C85 engine.  It is looking like the accessory case should come off and the oil pump clearances checked again. What else could cause this sort of oil pressure drop in a newly rebuilt engine?

[Cy Galley]

Think you have it nailed!

 

From: aeronca...@westmont.edu [mailto:aeronca...@westmont.edu] On Behalf Of Sam Burke

Sent: Tuesday, August 28, 2012 1:41 AM
To: aer...@westmont.edu
Cc: Pat Burke

[ginny wilken]

Sam, I had a similar problem when I rebuilt my C85. The shop that refaced the oil pump cavity screwed it up completely, and there was no pumping going on at all. I took the accessory case off as the engine sat in the plane. They filled and remachined it to tolerances, which I had to point out to them.

The only bad part was that they tried to fool me, saying I needed new oil pump gears. They had shown me some gears ostensibly from my engine, and said they were worn. However, I had match-marked my gears, and these were not them. I will not be using this shop for anything again. The actual machining was done and redone by ECi, who should have known better, too.

As far as I know, incorrect tolerances would be the only way pressure could stay so consistently low. You may find this site interesting; there is much discussion of oil pressure issues. The correct values for the pump gear clearances are in the back of the Continental engine manual.

http://www.bowersflybaby.com/tech/fenton.htm

ginny

All stunts performed without a net!

[Paul Anton]

The actual machining was done and redone by ECi, who should have known better, too.

 

I had the same experience with an accessory case done by ECI perhaps 10 years ago.

 

Paul

N1321A

N83803

2AZ1

 

[John Rodkey]

Another possibility is that the bearings are out of tolerances on the crank.
Either not enough pressure being created by the pump, or not enough back-pressure because of large clearances, I think.

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[j...@joea.com]

Or a combination of all of the below. Quite often the oil pressure in these engines is lost with the cam journals being too lose in the case and oil pressure just flows out. Have seen many cases where the mechanic never checks clearances in places like this.

You just do not know without opening it up at this point. Getting the oil pump back where it should be might get the pressure back up but what else is not right in there. If the mechanic just slapped things back together there are several other things that they could have missed.

One again....Something is not right with this engine and truthfully before I would pay a penny for it, its coming apart and being checked and measured again.

If it were my rear end paying the bill and sitting in the airplane, the mechanic who built the engine, AND an impartial observer of my choice, would open up the engine, check the clearances on everything and report back to the owner.

Joe A

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From:                         John Rodkey <pooba...@gmail.com>

Date sent:                  Tue, 28 Aug 2012 20:39:55 -0700

To:                             aer...@westmont.edu

Subject:                     Re: [f-AA] Low Oil Pressure on C85-12

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