Help Diagnose my Enigine spewing oil

[Jeev]

I am frustrated after working on this for a week with my A&P:

Aircraft: 1978 M20J IO-360 1750TSOH in 1992.  I have flown her about 250 hours in the last 12 months with not a single engine problem.  All comps are 74/80 or above and it is burning about a quart every 6.5 hours.

Problem:

Immediately after take off it starts to drop oil down the back of the engine (accy case) at an alarming rate of about 1quart per 2minutes.  During flight all oil temp, pressure and cylinder head temps are normal.  We cannot get it to do this on the ground after full power runups at operating temps.

What we have fixed:

Mag gasket was leaking it was replaced, prop governor was leaking and in need of overhaul it was overhauled, oil quick drain had a bad O ring so it was replaced.  After all this and test flights around the pattern each time it still pukes oil enough to trail white smoke and totally soak the belly.

Inspection shows the MAG and governor dry but oil dripping down the middle of the firewall out the gear door.

Again we cannot duplicate the problem on the ground.  Any ideas?  My mechanic is going to check the oil pan tomorrow and look closer for a crack in the case..  Worst case I am expecting an overhaul but due to the engine humming along perfectly except for this leak I am hesitant to spend $25k with out knowing exactly what is causing this.

Thanks in advance for your ideas.

Sanjeev

 

[laytonl]

Does your breather line have an anti-ice hole in it?  You could have a broken ring causing the crankcase to pressurize and blow oil out the breather and onto the firewall.

However, my best guess is either a cracked accessory case or a crankcase.  Accessory case is not too bad, other than the need to remove the engine to replace.

Good luck and let us know what you find.

Lee

 

[Jeev]

Thanks Lee - I will look into the breather tomorrow as you are the 3rd person to bring it up.

[Kwixdraw]

Oil leaks are tough to find after an in flight test run. Given what you are describing and have already done I think I would invest in a kit to add flouresent dye to your oil and the uv light to make it show up. I think you can get these pretty reasonably now through different sources. Clean your engine real well and ground run it a short time to warm the oil. I think I might also try to cinch the tail down to simulate takeoff attitude as much as possible. Check it with the light to see where it glows. Oil return lines can make a hell of a mess but I don't know if that would be attitude related.  Very curious like the rest of us.

[Kwixdraw]

Looked your post over again.... clean around the tach drive too, the seal in there can puke pretty good too.

[Mckipper]

I had a seal go on the back of the oil filter mounting plate. Also had the soaked belly and inside of nosewheel doors, could not find the leak only later did we find the fault when I saw a drop falling while adding air to the nose wheel.

 

My AMO told me there was an AD out on that seal.

 

[Jeev]

Update:

We ended up putting a ziplock bag over the governor and running it up and cycling the prop. Oil on the inside of the bag! The O/H'd governor was just installed and the leak looks to be coming from between the gov and the gov pad.

I will update with the end solution as my fingers are crossed and I am a little relieved concidering I was prepairing for a crack.

[mikefox]

If it is coming from the governor mounting pad, make certain that the governor was installed with a spacer plate and gaskets on both sides of the plate.  If it is not installed properly, it will not seat, and the loss of oil can be catastrophic.  Many mechanics do not know this, as only two engine installations use this spacer plate - the IO360 in the M20J and in the Cessna 177.

Take this seriously - we experienced just this on our governor, and there was a special service bulletin issued after a fatal crash following loss of engine oil on takeoff!

[jlunseth]

The suspicious thing to me is the white smoke.  That means you are burning oil.  Cracked ring or hole in a piston maybe?

I had a little experience with the quick drain in my plane.  It was not the o ring.  Small piece of plastic went in the intake side of the quick drain and was too big to exit, but blocked the drain from sealing so we blew out alot of oil.  But that drips onto the belly pan and then out from the belly, not higher up, and you would not have smoke.

[KSMooniac]

I bet his oil coming from the governor is simply getting blown onto the exhaust and smoking.  Hopefully the mounting pad issue is indeed all there is to the problem and you get many hundreds of hours more out of the engine!

General troubleshooting tip...always look at what was just touched when a problem arises.  It is highly unlikely, statistically speaking, for a new problem to manifest itself right after you work on the plane for some other reason.

[Jeev]

Quote: KSMooniac

I bet his oil coming from the governor is simply getting blown onto the exhaust and smoking.  Hopefully the mounting pad issue is indeed all there is to the problem and you get many hundreds of hours more out of the engine!

General troubleshooting tip...always look at what was just touched when a problem arises.  It is highly unlikely, statistically speaking, for a new problem to manifest itself right after you work on the plane for some other reason.

[Jeev]

Quote: mikefox

If it is coming from the governor mounting pad, make certain that the governor was installed with a spacer plate and gaskets on both sides of the plate.  If it is not installed properly, it will not seat, and the loss of oil can be catastrophic.  Many mechanics do not know this, as only two engine installations use this spacer plate - the IO360 in the M20J and in the Cessna 177.

Take this seriously - we experienced just this on our governor, and there was a special service bulletin issued after a fatal crash following loss of engine oil on takeoff!

[georgeb]

I fought a similar problem that took us 3 months to find....Same symptoms...on the ground, not a drop, no matter how hard it was run, but fly it for about 10-15 minutes and the entire pilots side of the cowl and subsequently the belly were full of fresh oil. After replacing oil hoses, cooler, 2 removals of the oilpan, all kinds of gaskets, we finally resorted to putting a dye in the oil and found the problem....I had a crack on a cylinder base just above where the cylinder goes into the crank. The leak/crack was hidden by the aluminum baffling that surrounds the cylinders as the base. The leak required the torque of the engine running as well as a couple of minutes to work its way through the baffling and out to where it covered other engine parts with oil making them seem like they were the culprits.....All along I had good oil temps/pressure as well as all my cylinder comps were in the high 70's....

Good luck!

George

 

[KSMooniac]

Could you tell us which shop did the O/H on the governor?

[tyrefoote]

Hi All ,

I also had a very simular problem on a 88 J that ended up being leaking 1/4 " Plug on the bottom of the prop gov. mounting pad.  I recall their being a un-used threaded hole in the very bottom of the mounting pad that is plugged with a 1/4 " plug that had worked loose.  Hope this is helpfull and good luck oil leaks can be labor intensive.   Ty

[Jeev]

Yep got the the governor back today.  The O/H shop pressure tested it and it was shooting oil all over the place! Makes me wonder if all they did was paint it, charge me $1000 and send it back!  Cost me a week of flying Southwest back and forth to Cali! Painfull! Looks like Ill have it back on Monday! 

[Jeev]

Quote: KSMooniac

Could you tell us which shop did the O/H on the governor?

[PWL]

I had an oil leak at Oshkosh this year, the source of which was not obvious at all.  The A&P in the emergency repair shop came over, used a can of white spray-on foot powder to cover likely joints and seams and in about 30 seconds of operation forund a hairline crack in the weld of the oil cooler.  Hope this is helpful for others.