I have a C5 w/ LS1, automatic and 220K miles with an engine oil leak. This leak is bad enough that oil leaks down onto the exhaust pipe and catalytic converters so bad that when you stop the car smoke comes up thru the hood. Very annoying.

It's not leaking at the oil pressure sensor or the cam positioning sensor...it's not coming from the top of the engine at all. Not the valve covers either.

My best guess is the rear main seal is the problem and this is after a couple of trips to the car wash to completely clean the region of the leak.

Car is on floor jacks 2 ft off the ground. With the exhaust system removed and looking up thru the bell housing lower port where the flywheel is, it looks rather dry.

Question: If the rear main seal is bad, wouldn't I find plenty of oil in this region? I know there is an aluminum cover that bolts to the back of the engine and possibly any oil leaking thru the rear main would be captured by this?

Are you positive that the oil isn't migrating from the front of the engine to the rest of the engine/car.

I ask this question only because I had a similar issue. My front cover, dampener seal failed and I had oil EVERYWHERE!!

The front cover dampener seal gets old/hard and abrasive and cuts a groove into the sealing surface of the dampener. POOF! Massive oil leak and it gets blown EVERYWHERE!

Time for a rebuild

Could be the rear cover plate. They are cheap but a major project to replace. Mine was making a huge mess look up my thead on it for some info.

Thanks guys for all your responses!

Bill, The front seal has a very small leak. This is something more from the back of the engine.

There is oil on the bottom of the starter, which made me look at everything above the starter, but I cannot find any oil leak coming from above. Valve cover gaskets are solid too.

If it is the rear main seal, would there be oil found inside the bell housing? Or would the rear aluminum cover plate mask that?

Simtech, I will look for your thread.

This has been a very puzzling problem.

Get a florescent dye kit and add it to the oil after cleaning the engine real well. Not an expensive item and handy to have!

The rear engine cover (similar to the front engine cover) is known to leak. Some of the covers had a porosity issues. I would GUESS that its leaking somewhere on or around that rear cover. YES, it behind the Bell Housing and flywheel and very difficult to inspect.

I looked back at my pictures but didn't take any of the rear cover after I got the drive train out of the way. If I remember correctly there wasn't much oil on the cover itself. It leaks at the top and runs down the side. Her as a link to my post.

https://www.corvetteforum.com/forums/c5-general/3780992-weekend-project-replacing-rear-cover.html

Simtech, your 4th picture down looks very similar to what the bottom of my engine looks like. Did your flywheel/bell housing are look "dry" when you looked thru the lower bell housing access hole?

Bill, you are correct about it being difficult to detect. I tried the dye and flourescent light technique but it's difficult with the exhaust installed.

It was a little oily but not as bad as I thought it would be. Looking through the access hole with the car running it looked like the leak was between the rear cover plate and the pan. I could actually see it oozing out. I tried pressing rtv into that space but it just ran over the rtv because it was coming from the top of the cover plate. From what I understand the channel at the top of the plate is under preasure. It does make a mess on the bottom of the car and smells bad.

Do you have anymore pics of what the oil mess looked like on the front? I'm experienced the same thing as you are describing and just want to make sure that it is the same thing before I tear into it

To drop the rear assy down, do you have to remove the rear mono spring as listed in the shop manual?

No u dont, the assy comes down as on piece.