Hello Everyone,
It has been a while since I posted about this problem. So here is an update. But first some background - I am a mechanical engineer. I make my living keeping old industrial machinery operating at a large power plant (500 MW power boiler, steam turbine, large rotating equipment, etc...) I have over 30 years of experience as an engineer in shipyards, chemical plants, and power plants. Although I have designed machinery, I am not a trained machinist or A&P but have worked with these type of people all my career. I have a better than average understanding of machinery and most importantly know my limits. I relate this because there was some discussion in peoples replies to my post about not knowing the original poster's (i.e. me) background. Some pilots have a lot of mechanical background, some don't.
Having said that, what started this thread was that my experience told me the IA who has maintained this plane for five years was wrong when he kept telling me that this oil drip was normal. I live in a residential airpark of over 100 homes and know most of the pilots in the neighborhood. The general consensus was that I am too fussy and that airplanes normally leak oil. Still my experience told me something was not right with this plane that I have flown all over the country since I bought it in 2009.
I respect the folks in TIC170A and the safety culture that is typically found here. So I posted this original question about the oil leak. After reading the replies to my post I decided to ground the aircraft until I was satisfied that I found the cause of the drip/leak.
I changed the oil, took the cowling off the plane, degreased, and washed the engine. Then I ground ran the plane hard enough to get the engine really warm. After that I put the plane in the hanger with paper under it and let it sit for a week while checking on it daily. I found that the plane developed a puddle of oil on the ground that continued to grow daily. This lead me to the source of the drip which appeared to be the front 5/8" plug and it's crush washer. So I pulled the front lower baffling. What I found was an un-airworthy patch on the bottom of the oil sump in front of the carburetor. The patch appears to be some type of epoxy with a fabric embedded in it. See the pictures below:
![C-145 Oil Sump 1.jpg (23.12 KiB) Viewed 16640 times Overall view of patch](./download/file.php?id=9539&t=1&sid=8e58ad0cf109b0ebe013313db30e3c6a)
- Overall view of patch
![C-145 Oil Sump 2.jpg (23.63 KiB) Viewed 16640 times Closer view of patch](./download/file.php?id=9540&t=1&sid=8e58ad0cf109b0ebe013313db30e3c6a)
- Closer view of patch
![C-145 Oil Sump 3.jpg (30.87 KiB) Viewed 16640 times Red arrow points to crack that is source of oil leak/drip](./download/file.php?id=9541&t=1&sid=8e58ad0cf109b0ebe013313db30e3c6a)
- Red arrow points to crack that is source of oil leak/drip
It is apparent that when the engine was overhauled before I bought the plane (according to the logs in 2004) the mechanic attempted to repair a bad sump by applying this epoxy patch. As I originally said, the plane has always dripped oil since I had it. But the drip appeared to be getting worse. It is my opinion that the patch was progressively failing, and eventually I suspect would have lead to an in-flight total oil loss and forced landing. I am not happy to find this development. However, that is balanced against being satisfied with myself for following my instinct. Most importantly, I am glad I didn't continue to fly and have an in-flight failure.
I want to thank everyone here - your posts helped convince me not to ignore this matter and keep flying the aircraft. Bruce, George, Voorheesh, C170b53, hilltop170, sfarringer and all the others - THANK YOU for taking the time to read my post and reply. I wanted to let you know the result of your replies.
Now, I am going to pull the sump and either replace it or repair it. There is another experienced IA in the neighborhood who rebuilds engines - he came by to look and is searching for a serviceable sump. In the meantime if anyone knows of a serviceable sump or a repair service, I would appreciate them letting me know. I am still trying to get this bird back in service so I can complete the instrument ticket before my 3/31/15 deadline.
Regards,
Pete P.
The better is the enemy of the good.
1959 C-172