Oil leak between crankcase halves

[gwcolwell]

1974 M20F Exec. IO3601A1A

Have had an oil leak for last several years. Getting worse. Time for an annual so I dyed the oil, ran the engine, and shot it with a black light. Oil leak is coming from between the crankcase halves, near the front of the engine, between the starter & alternator. Engine has approx 1800 hours.

#2 CHT is consistently 50 deg hotter than all others (which are even) during cruise. Have tested the CHT probes for 2 & 4 cylinders. they react the same to the same heat source.

Have seen a strange discoloration on a few cooling fins on #2 cylinder around the exhaust port. No other cylinders exhibit this discoloration.

Would appreciate any wisdom/experience.

[ELT]

Hi,

I had a 3 different Inspectors tell me I had a case leak at the mating surfaces. They called it corrosion control and to keep flying the airplane. I planned to put a GE cement on the case to stop the leak. However, when we removed the starter, servo and other stuff we found a cracked case. Not to really fault the other inspectors because the only way to find the crack was to remove a bunch of stuff. Case cracks are much too common on the IO360A1A. Check it !! but if you have 1800 hours your engine is telling you something. My engine was 700smoh but in18 years. When opened up the engine all that was good was the crank.

Good luck

Eddie

[TonyPynes]

Had this exact issue if it is indeed between case halves mine was on a recent overhaul so I really didnt want to split the cases. Had to eventually split cases for a taxi prop strike and they fixed the leak permanently. But prior to that I was able to stop it by applying sealant on the outside surface. It worked and the leak stopped. So it might be a temp fix. PM me and I will give more details.

[N201MKTurbo]

I have had luck stopping the leak using locktite ( I forget which number I used). Clean the area around the leak with MEK and then Alcohol. Apply the locktite it will be drawn into the crack and it sets without air.

In my case it eventually turned out to be a cracked case

[Alan Fox]

I sealed a continental case leak at the halves with proseal.... Not pretty , but no more leaks..