Oil leak on the back of an IO-360

[MV Aviation]

Hi everyone,

after a flight (M20E) last weekend I noticed some oil dripping onto the nose wheel. It was coming from the backside of the engine, dripping from the bottom onto the cowl flaps, and making its way backward to the wheel. It's definitely coming from inside the engine and it's not any spilled oil. Looking into the wheel case from underneath made clear that it had created kind of a mess in there. This has never happened before and the belly and wheel case were clean prior to the flight.

I followed the traces to the top part of the engine on the backside. I couldn't locate the origin exactly due to obscuring pipes and hoses, but I believe it's coming from somewhere close to the right mag. Has anyone had similar experiences and/or any advice?

Thanks.

Best, Marco

[tony]

did you recently time the mags?

[MV Aviation]

41 minutes ago, tony said:

did you recently time the mags?

no.

[carusoam]

Some things to get started...

Expect to find something as serious as a loose mag...

a well known experience comes from re-using the hardware that is a one time use only thing.  Star locking washers?

There are a couple of ways to detect better where the oil is leaking from.  UV dyes and powder?

There are a couple of things mounted on the back side of the case.  Mags, vac pump and a few other things...

Some things can get so loose before being noticed, you may be able to grab and wiggle something loose.

Hope that helps...

Good luck with the search.

PP ideas only, not a mechanic.

Best regards,

-a-

Edited March 16, 2017 by carusoam

[1964-M20E]

Check 2 things

1. prop governor mine was leaking with similar results to yours

2. check you oil cooler lines if the fitting into the engine is loose this will cause an oil leak.  Watch how the oil line is tightened to the fitting the tension of the oil line can work loosen the fitting in the engine over time.

 

 

[N201MKTurbo]

Is your oil filter loose?

[1964-M20E]

Oh wash the engine good with some var-sol and then some alcohol to completely dry it  then run the engine for about 5 minutes and carefully look for where the oil is coming from.

 

 

[jdrake]

+1 for checking both mag and prop governor seals.  Been there, done that.

[MV Aviation]

Thank you, Gentlemen, for your input.
I tried to wiggle both mags and the vacuum pump. Nothing moved. (doesn't mean that it's perfectly sealed, I know). My mechanic distance-diagnosed that it could be a loose mag, which may result in timing issues over time.
My first fear, before I opened the cowling was the prop/governor. However, the oil trace on the backside of the engine (starting very high) and a (relatively) clean situation in the front makes me doubt that this is the issue. Prop is absolutely dry.

I didn't check the oil cooler or the filter. Wilco + washing the engine. The backside is very hard to access due to all the accessories.

What let's me become suspicious is the abruptness with which is issue suddenly occurred.

Edited March 16, 2017 by MV Aviation

[Brian Scranton]

+2 for vacuum pump and/or mag seal, or oil cooler/prop gov fittings. Other than a crack in the case--those are pretty much the only places you'd see a leak high up on the back of the engine. 

[jetdriven]

I agree with the others here, wash the engine off very good with mineral spirits and a parts washer then add some UV dye to the engine. Run it a few minutes and then go over it with a black light that stuff is great

[Browncbr1]

Don't forget to check oil dip stick where is screws into the case.  

[jnisley]

I had a very annoying leak on the back side of my engine several years ago, it ended upcoming from a plug on the bottom of the prop governor. (see pic)

[flight2000]

28 minutes ago, MV Aviation said:

My first fear, before I opened the cowling was the prop/governor. However, the oil trace on the backside of the engine (starting very high) and a (relatively) clean situation in the front makes me doubt that this is the issue. Prop is absolutely dry.

These two have nothing to do with each other.  I had a leak from my governor on my M20E after it failed and there was no visual up front on the prop of anything going wrong in the back.  What would lead you to believe that a leaking prop would be an indication of something failing up stream in the system?

Cheers,

Brian

Edited March 16, 2017 by flight2000

[jnisley]

Even though the oil leak was was coming from the plug in image2 which is above image1 it accumulated below the oil sump strainer plug, dripping down the back of the firewall into the gear well and belly of the plane. We first removed and checked the strainer plug (image1) but it continued to leak so we removed and reinstalled the plug in image2. Problem solved!

[Browncbr1]

4 hours ago, MV Aviation said:

 

 

Marco, does the convoluted foam and insulation on the firewall make a noticeable difference in cabin noise?

[MV Aviation]

4 minutes ago, Browncbr1 said:

Marco, does the convoluted foam and insulation on the firewall make a noticeable difference in cabin noise?

I don't have any reference, so I can't tell. I bought the plane with all the insulation installed. The inside is completely covered, even the (in this picture removed) side panel.

[carusoam]

3 hours ago, jnisley said:

I had a very annoying leak on the back side of my engine several years ago, it ended upcoming from a plug on the bottom of the prop governor. (see pic)

Jnisley, 

Fyi or question...?

Why does it look like the torque seal paint on the bolt heads seems to be indicating something has moved in this picture?

Sorry gents, for going off track...

best regards,

-a-

Edited March 16, 2017 by carusoam

[neonbjb]

I'm looking at a similar leak that has popped up on my plane recently. My A&P and I have found that the oil seems to be accumulating on the bottom of the governor (and the other accessories are tight and dry) so that is the prime suspect.

Were you guys able to access the plugs / seals on the governor without removing the whole engine? Any tips? It's extremely tight back there..

[jnisley]

1 hour ago, carusoam said:

Jnisley, 

Fyi or question...?

Why does it look like the torque seal paint on the bolt heads seems to be indicating something has moved in this picture?

Sorry gents, for going off track...

best regards,

-a-

According to the attached pic it appears like my mechanic torqued the bolts and hadn't resealed them yet, it's being annualed as we speak so I'll confirm my assumption.

[jnisley]

48 minutes ago, neonbjb said:

I'm looking at a similar leak that has popped up on my plane recently. My A&P and I have found that the oil seems to be accumulating on the bottom of the governor (and the other accessories are tight and dry) so that is the prime suspect.

Were you guys able to access the plugs / seals on the governor without removing the whole engine? Any tips? It's extremely tight back there..

We had to move several hoses of to the side to get to the leaking plug but nothing major.

[flight2000]

They did have to loosen my engine mounts and some other stuff to get the governor out on mine.  Damn thing is packed in there and is the single worst item to have fail from a replacement/overhaul perspective IMHO....

Cheers,

Brian

[Marauder]

Hi everyone,
after a flight (M20E) last weekend I noticed some oil dripping onto the nose wheel. It was coming from the backside of the engine, dripping from the bottom onto the cowl flaps, and making its way backward to the wheel. It's definitely coming from inside the engine and it's not any spilled oil. Looking into the wheel case from underneath made clear that it had created kind of a mess in there. This has never happened before and the belly and wheel case were clean prior to the flight.
I followed the traces to the top part of the engine on the backside. I couldn't locate the origin exactly due to obscuring pipes and hoses, but I believe it's coming from somewhere close to the right mag. Has anyone had similar experiences and/or any advice?
Thanks.
Best, Marco

Marco - check at the base of the oil dipstick tube. Mine leaks there.


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[Bob_Belville]

9 minutes ago, Marauder said:

 

 

Marco - check at the base of the oil dipstick tube. Mine leaks there.


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I think that's the 1st place to look. I seem to need to take mine out, clean and replace the o-ring every other annual. And I've seen it on other Mooneys in Lynn's shop. Since the "stand pipe" is plastic I'm careful not to over torque it. When checking the oil level it's easy to unscrew the pipe, at least to the limit of the safety wire.

[jetdriven]

The factory dipstick tube gasket is very thin, made of paper, and act of loosening the oil dipstick cracks the gasket loose and it's just a crappy design. But if you get a small O ring and install it on the dipstick tube, about a 1/16th of an inch wide version, and torque that down and safety wire it, it was withstand movement without leaking.  Mine has been dry for three years now.

Edited March 17, 2017 by jetdriven