Engine oil leaks

[rbs4159]

My A&P and I are going crazy trying to eliminate oil leaks on my '68 C model. So far they've repaired a couple of cracked fittings on the rocker drains, re-sealed the oil cooler lines, replaced a gasket on the vacuum pump, sealed a couple of crankcase through bolts and replaced the crankshaft seal - twice! (the wrong spring was put in the first time) and 3 years ago the oil pressure regulator was removed to replace a cross-threaded crush gasket. The leak, oir leaks, seem to come from the front part of the engine. It's better now and the leaks are smaller, but every time I fly it, there's still a drop on the rear of the starter and the front oil pan bolts, and a small pool of oil in the bottom cowl. Anyone have any suggestions for leak sources that we might be overlooking? On another subject, I had to replace a Kelley Aerospace lightweight starter after only 3 years and about 300 hours. Anyone else have this experience? Thanks for any input

[MooneyMitch]

Just some more thoughts for you. Do check proper torque of all crankcase through bolts. Then seal along the crankcase seam, top and bottom. I believe some have used The Right Stuff from Permatex . Check intake gaskets too. Cylinder oil return lines/fittings, both ends. Use Neoprene valve cover gaskets.

Also, clean entire engine compartment with mineral spirits, rinse with water. After all is dry and clean, run the engine for a few minutes. Then look for tell tale signs of the leak

[TonyPynes]

Beyond the usual suspects of crankcase seal, prop seal, and loose bolts check the seam at the lower front of crankcase as it is prone to leaks.

[Sabremech]

Your A&P probably knows of this old trick, but clean the engine then run it for a short period of time. Use a black light to look for the source of the oil leaks. The oil will glow under the black light. This may help you find the nagging leak.

[kerry]

I 2nd the mineral spirits idea. I apply it with an air compressor. I found my leak within seconds of starting my engine.

[BigTex]

Removed post.

[gwcolwell]

Similar issues. M20F Exec. In real life I (and my brother) own/operate a medium/heavy truck franchise. I run the shop. We use an oil dye (cummins part # 3376891).. This dye is very concentrated and appears bright yellow under a black light. Small bottle normally treats 10 gallons of oil. I use the whole bottle in my Mooney and have successfully identified multiple leak areas successfully. Have addressed most with the exception of the one between the crankcase halves.

[DaV8or]

Check intake gaskets too.

Which intake gaskets? Why would the intake have anything to do with engine oil? Does it leak down through the valve guides? Just wondering because I now have oil on my intake manifold bolts and can't figure out where it's coming from. Is there any way to prevent this engine from beating itself to death? I bought a plane to go flying, but I'm finding it's more about fixing.