M-10 C-90 Oil Leaks

Good to know. Will probably do it next annual. Thanks.

You don't have to pull the motor to get the oil tank off, I did mine ( it was cracked) and didn't even have to pull the lower cowl, just the carb airbox to get some need clearance,

It's good that you found it. My O200 might have a similar leak since the pre-purchase inspection mentioned an oil leak onto the tank from an unknown source. I thought it might be coming from the filler cap so just wipe it off before each flight after checking the oil level. We thought the O-ring at the base of #4 cyllinder was leaking so had that replaced to no avail, there is still oil that streaks the left cowling. It goes in for annual next month so hopefully discoveries can be made and corrected that won't break the bank. Otherwise as long as it's not safety of flight, take along some wipes and call it anti-corrosion treatment.

After working on darn near EVERYTHING in the engine compartment, I finally found the oil leak. I'm sure there were additional leaks and replacing all the gaskets and seals made the whole compartment less messy, but the leak was between the case and the oil "kidney" and resealing that would pretty much require pulling the motor so I'll just live with it for now. If we ever do need to pull the motor, it WILL be sealed.

I did get the Mitchell oil temp gauge and sending unit which, according to the ads, was PMAed for most airplanes (Cessnas probably are) but I will have to get a 337 to install it in my M-10. I ran into the same issue with the LED landing and taxi lights. I have the panel upgraded so will get to all this other stuff later. I want to fly for a while.

When I got my M-10, it required a lot of work. The C-90 ran okay but had oil leaks around the starter, the generator, the mags, the front prop seal, and oil temp fitting. I replaced the starter with a lightweight Skytech Starter with new gasket. I replaced the generator with a new 40 amp alternator with new gasket. We replaced the front prop seal. I installed overhauled Kelly Aerospace mags with new gaskets. I installed a spin on oil filter.
The one leak I could never stop was around the oil temp sending unit. It doesn't leak much, just enough to leave a small streak on the right side of the airplane. We have replaced gaskets but that doesn't seem to work. I decided to change the way the unit works. I am installing a Mitchell oil temp gauge with an electronic sending unit. It is a sealed unit and with a new gasket should end the issue. I'll let you know how it works.