Very Low Oil Pressure In Flight

[Stetson20]

I took my wife up for a 1.0 flight today. 4500 vfr sight seeing tour over western MI. As we headed back to the airport, I noticed oil pressure had dropped to 30psi and prop rpm sneaking up to 2700. At cruise, I had set 2500 rpm and 22 mp. Leaned to about 20 lop at 9.0 gph.I noticed the oil pressure around 30 and as I continued to home airport, it steadily went down, eventually bottoming around 22psi. I had to pull mp back to 20 to keep prop rpm below redline.

Did a precautionary profile landing at home base. I was a little nervous, so I carried too much energy in to landing and bounced. I did a go around, and when I added full power, the oil pressure went to 60 (better, but still low) and prop rpm did not overspeed. 

Ive flown the plane a total of approx 15 hours since purchase. Have added 3 quarts of oil. 

Going to have the oil filter removed and cut open to look for metal. Also plan to send oil sample to Blackstone. I hope it's not the engine. 

Thoughts?

[RLCarter]

clean the screen as well

[carusoam]

The governor not governing is a hint that air is probably going into the governor's oil pump.  A governor failure on Mooneys fails to high rpm.  (Except the Missile and Rocket?)

The missing oil is going somewhere...

1) 3 quarts out the exhaust pipe will leave a mess on the belly.

2) if an oil ring is broken the lower spark plug will show signs of oil all over it.

3) rough cylinder surfaces can be refinished. They have a tendency of allowing oil to escape. All four may be equally trying to burn oil...

4) any Compression data available?

5) any pictures from inside the cylinders available?

6) any oil spilled all over the cowling inside? Sometimes leaky seals and oil return tubes have a tendency to splash oil around.

7) spend some time finding where all the oil went....

PP thoughts only, not a mechanic...

Best regards,

-a-

Edited May 12, 2017 by carusoam

[Dream to fly]

I had a very similar experience after purchasing my M20F.  On my final leg of the return from purchase trip my instructor and I started to notice the oil pressure drop and rpms fluctuate.  after being marshalled in to Bismarck, ND  I was asked if I needed oil and I must have had a look on my face like how did you know we had oil problem.  Then I got out of the plane and knew why he asked.  The oil cooler ruptured and I leaked about two or three quarts down the side of the plane.  I should have looked into it before that last leg because there were signs before that.  In 8 hours of flight the plane had "used" 1 - 2 quarts of oil and the belly was not dirty.  For whatever reason the engine oil cooler was dripping the oil in such a way that the bottom of the middle of the  left wing was slimed and the tail.  My fault for not doing a good inspection.  I'd look for leaks before thinking the worst.   Just my two cents.

[LANCECASPER]

10 hours ago, Stetson20 said:

Ive flown the plane a total of approx 15 hours since purchase. Have added 3 quarts of oil. 

Going to have the oil filter removed and cut open to look for metal. Also plan to send oil sample to Blackstone. I hope it's not the engine. 

Thoughts?

What were the compressions on each cylinder during the pre-buy?

[flyboy0681]

Hate to say this, but Lycoming highly recommends a tear down when pressure drops below 55psi. I had this happen to me last September and the result was an overhaul. In the end an exhaust valve stuck and all of the oil burned off.

[Yetti]

How many qts are you running your engine at?

What does the belly look like?

[Stetson20]

3 hours ago, LANCECASPER said:

What were the compressions on each cylinder during the pre-buy?

I'll have to go back and look. They were in the normal range.

[Stetson20]

2 hours ago, flyboy0681 said:

Hate to say this, but Lycoming highly recommends a tear down when pressure drops below 55psi. I had this happen to me last September and the result was an overhaul. In the end an exhaust valve stuck and all of the oil burned off.

Is there a service bulletin or something that references this? Or did they tell you over the phone?

[Stetson20]

1 hour ago, Yetti said:

How many qts are you running your engine at?

What does the belly look like?

6 to 7.. I need to look at the belly. I was pretty distracted yesterday when I landed. I DID take off with 5 qts yesterday, as I intended to add oil when I topped off with gas at the completion of the flight.

[Bartman]

I would not take off with 5 quarts on the dipstick.  The oil cooler dissipates heat, but if the oil recirculates and retains heat due to smaller quantity of oil then I think it will be less viscous and may provide less oil pressure.  Approach and landing would cool the oil and may bring the pressure back up...for a while.

I'm no expert, but that's my story and I'm sticking to it.

[Yetti]

I run mine between 6 and 5 qts.   The indicator that I have that it should have oil is the oil pressure gauge will do a small movement.

7 you may have just pumping it overboard.

The belly will tell the tale

You may also want to pull the cowl and check for leaks.   valve cover return lines are a source of leaks in many ways.  The clamps on the rubber pieces, the rubber pieces, the fittings on the head, the alum tubes when they are cut by the safety wire that replaces the rod.

[Guest]

I prefer to run mine between 13 & 15 quarts, never below 12.

I too am curious about the Lycoming reference to 55 psi.

Clarence

[flyboy0681]

43 minutes ago, M20Doc said:

I prefer to run mine between 13 & 15 quarts, never below 12.

I too am curious about the Lycoming reference to 55 psi.

Clarence

I'm trying to see if it's still on my laptop, which I needed to reload earlier this year.

[peevee]

58 minutes ago, M20Doc said:

I prefer to run mine between 13 & 15 quarts, never below 12.

I too am curious about the Lycoming reference to 55 psi.

Clarence

I like mine at 10.5, or rather our engine likes 10.5

[flyboy0681]

1 hour ago, M20Doc said:

I prefer to run mine between 13 & 15 quarts, never below 12.

I too am curious about the Lycoming reference to 55 psi.

Clarence

It's Service Bulletin 399A. This supersedes 399 which contained more information but I can't find a copy of it. 

For the IO-360, the minimum oil pressure is 55psi.

Any time oil pressure falls below the minimum level, land the aircraft as soon as possible and diagnose to determine the root cause according to the following protocol progressive steps

f) If the oil pressure indication system is functioning correctly and oil pressure loss/oil starvation has been confirmed, remove and disassemble the engine and perform a complete inspection.

[Guest]

Here is the referenced SB.  

https://www.lycoming.com/sites/default/files/Action to Take If Loss of Oil Pressure.pdf

The SB does not give an actual oil pressure value.  I would take it that if the pressure fell below a minimum set by the engine operation manual or the airframe PoH the SB would come into effect.  The airframe PoH trumps the engine operations manual.

Clarence

[Yetti]

There is an AD from Lycoming on oil pump gears.  May be something to check the logs for...

[Guitarmaster]

I prefer to run mine between 13 & 15 quarts, never below 12.
I too am curious about the Lycoming reference to 55 psi.
Clarence

Sheesh!!! I only run 10 in my Duramax!

Of course, the 11.7L motor on the Comanche is about twice the size of my truck engine. .


Sent from my iPad using Tapatalk

[flyboy0681]

2 hours ago, M20Doc said:

Here is the referenced SB.  

https://www.lycoming.com/sites/default/files/Action to Take If Loss of Oil Pressure.pdf

The SB does not give an actual oil pressure value.  I would take it that if the pressure fell below a minimum set by the engine operation manual or the airframe PoH the SB would come into effect.  The airframe PoH trumps the engine operations manual.

Clarence

I think you will find it to be 55psi

[gsxrpilot]

I read that to say that if you lose oil pressure but after investigation there is nothing wrong with the oil system... THEN you need to tear down the engine. Which kinda makes sense since you need to find the problem. But if the problem is with the oil system, then just fix it and move on.

[Guest]

I don't have an E model PoH, but this is the excerpt from the 360 operators manual., it does say 55 psi.  

Clarence

[wpbarnar]

Inspect the ball and seat of the oil pressure regulator.    A very small piece of trash between the ball and seat can cause a large drop in oil pressure.   If no trash is found rotate the ball 180 degrees as it will wear slightly where it contacts the seat.

Bill

[flyboy0681]

3 hours ago, M20Doc said:

I don't have an E model PoH, but this is the excerpt from the 360 operators manual., it does say 55 psi.  

 

On my J, the green band is very narrow on the oil pressure gauge. To me that says the manufacturer means it.

[Cyril Gibb]

On 2017-05-11 at 11:18 PM, Stetson20 said:

As we headed back to the airport, I noticed oil pressure had dropped to 30psi and prop rpm sneaking up to 2700. At cruise, I had set 2500 rpm and 22 mp. Leaned to about 20 lop at 9.0 gph.I noticed the oil pressure around 30 and as I continued to home airport, it steadily went down, eventually bottoming around 22psi. I had to pull mp back to 20 to keep prop rpm below redline.

Some unasked questions that may narrow down where you go from here:

How much oil was in the crankcase when you landed?  The POH would probably say 6 qts minimum, but Lycoming says (per certification standards) that 2 qts is the safe minimum.  If you still had at least 2 qts on landing and didn't perform any aerobatic maneuvers, your oil pickup wouldn't have been unported.  If it was less than 2 qts, the bearings would now be suspect.

Did your oil temperature increase as the pressure decreased, or did it stay more or less stable?