High oil pressure beyond limits

[LARRYDLM]

I have a Mooney Ovation 2 with G1000. Recently after a 2 hours flight, oil pressure started to increase significantly and went into the red (oil temprerature and everything else was ok) and I decided to land to the nearest aiport. After 1 hour I decided to take off and after 30 minutes same problem (oil pressure in the red) again and decided to land to another aiport. When I read the POH, there is no reference to such situation (only low oil pressure). When I spoke to my mechanic who check the plane about this his answer was it should be a faulty sensor. Has anyone experienced such issue?

thanks in advance.

Larry

[N33GG]

I am aware of a similar incident, couple of years ago, with a Cessna 180, brand new engine, first flight home, and the pressure was so high the filter blew apart.  Over pressure can happen, and should be taken very seriously... it is not always a sensor!

[N201MKTurbo]

About the only thing that could cause that would be a stuck pressure regulator, or a clog in the pressure regulator exit port.

[takair]

Not familiar with your specific engine, but I thought a spun bushing (oil holes don't line up) or blocked oil passage could also do it. Start with the simple things suggested, but take it seriously.

[rob47v]

About the only thing that could cause that would be a stuck pressure regulator, or a clog in the pressure regulator exit port.

Absolutely correct! oil press reg is a simple check ball and spring in majorities of cases. If the the check ball becomes dis-formed and gets stuck in the port oil pressure will increase and can cause bearing failure in some cases, in the lucky event your filter will blow and as long as the engine can be shut down quickly its a recoverable situation.       

[Guest]

Perhaps a defective oil pressure transducer is the cause of the trouble. If it is repeatable after a long flight have an accurate pressure gauge connected in parallel with the existing transducer and run it up for comparison.

Clarence

[rob47v]

Perhaps a defective oil pressure transducer is the cause of the trouble. If it is repeatable after a long flight have an accurate pressure gauge connected in parallel with the existing transducer and run it up for comparison.

Clarence

Unless this is a different animal it should be a wet gauge. Tho even wet gauges will be erroneous when they go bad. I've seen that but on the opposite lwr pressure than actual, never on the higher ,but anything could happen!!!   

[Guest]

The airframe in question is G 1000, hence transducers.

Clarence

[rob47v]

Efis yes it will have a transducer absolutely. Don't own an Ovation nor ever worked on one. But even with a transducer failing to the erroneous high seams weird, I've just never seen such failure, intermittent btw low and high yes, to the low yes but never to the high. Interesting, please keep us posted   

[Bill_Pyles]

I don't have any answers, but I do have an experience to relate from yesterday, June 14. I have a 1980 M20J and  I changed the oil and filter last Friday, and yesterday I flew from my home base, Phoenix DVT to LVK in northern CA, about a 4 hour flight.  I cruised at 8500, 23 MP and 2460 RPM.  On two occasions, the first occuring after an hour of flight and the second occuring at 2.5 hrs, I got a slow rise in oil pressure (indicated by the original analog gage) into the yellow.  In both cases I reduced power and RPM and the oil pressure gradually returned to the middle of the green, where it usually runs.  In neither case did the oil temperature rise with the supposed rise in oil pressure.  I also have an EI gage but the oil pressure on reads either stupid numbers such as 0 PSI or 22 PSI, or it sometimes reads expected or normal values such as 75 or 80 PSI.  In neither case where the analog gage indicated high pressure did the EI gage also indicated high pressure.  The EI gage always either reads "normal" number steadily or it reads "stupid" numbers such as 0 or 6 or 17 PSI, erratically.

 

I have spoken with Mark Roush at Top Gun and Don Maxwell and they both said I should cut the filter open to check for metal. Mark said the worst case scenario is a crank bearing has spun, blocking the oil feed holes and causing a pressure rise.  I don't see how a bearing would spin so the holes are out of alignmenent and then re-align for an hour or more of flying.  In reading Mooneyspace I see theories of the pressure relief valve sitcking, but I think it would be more likely to stick open than closed which would cause a drop in oil pressure. 

 

Since almost a year has passed since the last post in this thread, does anyone else have any theories or stories that may contribute to the body of knowledge on this topic?

 

Bill

[Piloto]

I had a similar problem with the gauges and found that cleaning the pressure transducers (fuel and oil) inlet with carburetor cleaner (from Pep Boys) helps on solving the problem.

José

[N201MKTurbo]

I had an engine that spun a bearing. It kind of did that. If it is spun it will make a lot of metal.

[carusoam]

Isn't a spun bearing a one way trip? No realigning after the event...

Followed by lack of lubrication to some important spots and lots of metal, hot temperatures, and funky vibrations...

Fortunately, my experience only comes from my lawn tractor.

But it sounds like good news for you...?

Check your oil, if it smells burnt or has turned black in this short period, that would be bad news...

Keep in mind, I'm a PP, not a mechanic, but I did replace my own engine on my lawn mower....

Best regards,

-a-

[PaulB]

Here are the suggestions from the Lycoming Troubleshooting Guide.

[Andy95W]

My gut feeling is that you have an indication problem in the stock gauge. I think I would trust the transducer driven EI instrument (when it isn't giving you stupid readings).

After confirming you don't have a problem that will kill you (by cutting open your filter AND checking your suction screen), I would clean out your stock oil pressure line and gauge like José said. I think it's possible you have either a fleck of something or a bit of sludge that blocks off pressure until you change something in your engine operation that then allows it to move and unport the gauge.

[Bill_Pyles]

Here's what happened yesterday:  I flew the plane 30 miles from LVK to SCK where Top Gun is located.  On this hop, both the stock gage and EI read normal, with the EI showing 82 PSI.  We cut the filter apart after four hours of flying and it was pristine--not even carbon flecs.  Turns out the transducer for the stock gage was mounted and grounded to one of the engine mount tubes.  Whereas whoever did this did scrape most of the paint (or powder coat) off the tube, the tube had some rust on it and the x-ducer mount (just a thin metal strap) was not completely tightened on the tube.  Since the gage is sensitive to the quality of the ground, we proved that increased resistance i.e. grounding through rust/paint caused the gage to occasionally read high due to the higher resistance.  Joe at Top Gun (great guy) ran new ground wire to the firewall and he also re-grounded the transducer for the EI gage.  I flew the plane back to DVT (in 3:35 due to a little push) and both gages performed flawlessly and with no weird deflections.  When the oil temp got over about 205DF, the OP went to 77PSI.  When I cooled the oil to 190, the OP when back up to 80-82. 

 

So...I learned something about my plane, I believe I now have two functioning oil pressure gages, and I have confidence that the seemingly high pressure reading was caused by nothing more than variable resistance due to a poorly installed grounding scheme for the stock oil pressure transducer.  I should have taken photos for y'all....

 

Thanks everyone for chiming in.

 

Bill

[RobertE]

This info has been really helpful. Let me ask a follow-up.

How high is too high? When cold I'm routinely in the red and, once warm, in the low yellow or high green. My A&P isn't in the slightest concerned, figuring it's a slightly oversensitive sensor. I'm vaguely concerned, although this condition has persisted for years.

[Guest]

Some time ago Lycoming raised oil pressure limits to 115 PSI, airframe gauges do not reflect this. Higher oil pressure at initial start is normal. I do not allow my oil pressure to exceed airframe limits as I run it up, a few extra minutes of warm up will bring the pressure down.

In cruise with the temps normal you should expect oil pressure to be in the green range.

Clarence

[M016576]

I had the same thing happen with my old Jbefore I got a digital engine monitor: just like you say- it was a loose ground to the old stock gauges.

Got a digital engine monitor now... Haven't seen any loose ground issues since.

[Bill_Pyles]

This info has been really helpful. Let me ask a follow-up.

How high is too high? When cold I'm routinely in the red and, once warm, in the low yellow or high green. My A&P isn't in the slightest concerned, figuring it's a slightly oversensitive sensor. I'm vaguely concerned, although this condition has persisted for years.

You may very well have a ground wire that is attached to something corroded or rusty, as I did.  The rust increases the resistance and increased resistance shows up as a higher pressure indication.

[KSMooniac]

Some time ago Lycoming raised oil pressure limits to 115 PSI, airframe gauges do not reflect this. Higher oil pressure at initial start is normal. I do not allow my oil pressure to exceed airframe limits as I run it up, a few extra minutes of warm up will bring the pressure down.

In cruise with the temps normal you should expect oil pressure to be in the green range.

Clarence

Also on the Lycoming, higher is better in my opinion, unless caused by a spun bearing or other obstruction.  Lycoming relies on a very poor oil path through the lifters and pushrods to get oil to the rocker boxes and valves.  Higher pressure will mean more oil delivered to the valves, which is a good thing.  The Bravo engine got the Bravo mod (and hence the new name instead of TLS) that plumbed hoses directly to the heads to help keep valves cool and I wish we could add that mod to the angle valve 200 hp engine as well.  It certainly would help.

 

The newer (post 94) Cessna models with Lycoming engines have much higher oil pressure (80-100 psi green arc I believe) to help with valve wear.  Lycoming (and Cessna) did not promote the change when it was introduced since acknowledging that issue might open a can of worms for owner with legacy engines.  

[jetdriven]

My factory engine runs 95 PSI on the factory gauge and ~105 on the first takeoff of the day. They set the oil pressure at the factory. I called their rep and he said be careful, you might blow out the crankshaft seal in the front with all that pressure. I asked him why a 172R won't and he couldn't tell me. I didn't change the oil pressure either.

[N601RX]

I thought the newer models with the higher oil pressure limit added a bolt on plate that retains the seal.

[N201MKTurbo]

It's funny that the Lycoming guy would say that high oil pressure would blow out the front seal when the prop governor oil pressure goes through the front main bearing at up to 400 PSI.

[Andy95W]

My factory engine runs 95 PSI on the factory gauge and ~105 on the first takeoff of the day. They set the oil pressure at the factory.

Mine is exactly the same (550 hours on a G&N overhaul). I had been a little concerned, because that puts it up in the yellow/red on the oil pressure gauge.

Sure was glad to see a previous post that told of the new red line limit of 115, determined by Lycoming. Thanks for the peace of mind!