Rear engine oil leaks

[Jhogan0101]

Im having a hard time locating source of rear engine oil leaks.
After flight seeing a good amount of oil on the pilot side rear cowl under the tail cap.
Inside looks wet on the upper exhaust tree, pilot side.
Not seeing any evidence of leaking on the top half of engine.
Ive tried looking at the engine while running with the cowl disassembled and dont notice any leaks.
Does anyone know of any good strategies to try and hunt down this leak(s)?

[RandyArizona]

No "special" strategy, just the usual, clean, dry, check, re-clean... etc.
However, I had the same issue once, turned out to be the alternator shaft oil seal.
Sent it off for overhaul, came back, and dry engine.
Good luck.

[Joes]

Use foot spray powder, pulls oil out and changes the color of the powder. Easily identified, been using this method for 30 years.

[Rick Erwin]

Check the screws on the rocker box covers. They should be torqued to 25 in/lb initially, then retorqued to 20 in/lb thereafter.

You can also get an additive for the oil that will fluoresce under a black light.

Rick

[TomM]

The rear engine is hard....the way the air swirls around makes it difficult to figure things out. I have been chasing it, and while I have reduced it, I have not been able to totally stop it, so I gave up. I replaced just about every gasket that can be replaced without splitting the engine. I even followed some advice from the Mooney 231 group. Still leaks and leaves black smears coming out of the bottom of the cowl flaps and the cowl to fuselage joint. The aluminum rubbing together makes even new oil look like crap seeping out the cowl joints.

The color of my plane makes the oil only slightly less visible than a white one, but still there. And it only takes a few drips to make it look terrible back there.

Like I said, I gave up and just carry a spray bottle of degreaser and paper towels and clean it up when I land. I just tell people its like a radial engine.....the only time it doesn't leak is when its out of oil 🤣

Best of luck!

[Jhogan0101]

Well after jamming many towels in many places and running up/checking the towels.
It seems that the leak is on pilot side between cylinder 1 and 3.
When flight air blows down it makes a real mess inside this side of engine.
Ive included a link to the drip.
Ive looked topside of the engine and do not see any leaking.
Could my cylinder be leaking between the heat fins?
Has anyone else seen this?

https://ibb.co/Fm0CJ3W

[Kim Geyer]

It can leak there if the cylinder is cracked. I would remove that piece of baffle, pressurize the cylinder and soap check it for leaks. You may have a head fixing to separate from the barrel

[TomM]

Unfortunately, I have seen this personally, and to more of an extreme than Kim mentioned on my front engine.............so remove some of the items in the way and do a good check. I good borescope may help to get in tight places without having to remove a bunch of stuff. Of course these are extreme examples, but they do happen so you need to look. Keep us posted!

[Jhogan0101]

I removed the baffles today and good news looks like cylinder is not cracked.
Looks like the leaking is coming from the base of #3 and #1 cylinders.
Lots of wiggling when running.

[Jhogan0101]

After retorquing the cylinder base nuts it looks like both the 1 and 3 cylinder have a small crack behind where the CHT probe is.
The leak on 3 is worse, drips once every 3 secs or so.
I will remove both and exchange w j&j or gibson.

[mshac]

Pics if at all possible, please.