Trying to track down a annoying oil leak (enough to leave a small spot on my floor overnight). Its in the common area between the engine and bellhousing. I removed the inspection plate and look mostly clean inside with the exception of the "floor" of the housing which had a pretty good layer or oil and grime. Does this sound like a bad oil sump gasket or a leaking rear main seal or cam shaft seal? See pictures below. I would think there would be more of a mess inside if it was the rear main seal...

 

I have the same leak, however I think it could be coming from oil pan gasket or maybe up top from the valve cover gasket. I replaced both when doing head gaskets, oil pump, etc (all those good things ).
I opened my cover plate inspection and had some gunk on it along with some orange plastic shards (who knows what that is... have to post photos).., but looked clean up towards the rear main seal.
I think there is a post on the board with diagnosing this leak, I'll see if I can find it.

Have you replaced your oil pan gasket or valve cover gasket lately?
Just wondering.

 

Valve cover gaskets are new within the last eight months. Didnt notice any oil around the top of the engine, seems to be all from the lower, but I'll double check. I believe it is my oil pan gasket but thought it also could be the rear main seal, but I was a little surprised to see the insides of the bell housing so clean (minus the bottom).

 

Could be your Oil Pan Gasket and if all is clean on the upper side ie. valve covers, rear area of intake valley gasket (which is impossible to see unless you pull the plenum).

I had a leak following an engine rebuild just like you do. Started at the top side and found nothing. Pulled and replaced the sump gasket which still did not correct the problem.

So I had figured it must have been the Rear Main that I installed incorrectly. Just had the engine out for yet another head gasket R&R and upon inspection of the Rear Main it was dry as a bone. What turned out to be the problem was the Cam Plug which is directly above the Main Seal. Once I removed the plug it was evident that Turner Engineering didn't place any RTV Sealant on the plug.

So I replace the plug and main seal and have no leakage out the back. I do have some minor oil that is coming from two or three of the oil sump bolts which I'll live with.

 

Where did you find oil? Where the insides of the bell housing covered? I though it could be the rear main or the cam plug too, but I could only see a tiny part of the back of the engine through the inspection port and it was clean...

 

yeah you really can't see much from the inspection port, from what I could see it looked clean, not like oil was all over the torque converter. With the engine out its an easy job of course.

 

I hate to revive an old thread but I've got the same exact leak. Just got done replacing head gaskets, valley gasket, rocker cover gaskets and the oil pan gasket. Inside of the bell housing is dry as a bone but I've got oil around the back bottom of the oil pan where it mates to the bell housing. All the bolts are torqued correctly. I applied the sealant to the gasket front/back... Where the hell is it coming from?!

2004 DII 125K miles with Rotella 15-40

 

I got a cheapo USB borescope and checked out further up the back of the engine block a while back. This confirmed that my rear main is not leaking. It has to be the oil pan where it mates to lower bell housing. I checked with the borescope through the drain plug to during an oil change, I can see RTV squeezing out on the inside seal. Could it be just poor design and no matter what it will eventually leak again? I believe someone before me must have dropped the pan cause it was so clean, no sludge what so ever...unless the Rotella is doing a heck of a job.

 

Just snug up the oil pan bolts carefully. That may be all it is.
Check for leaks at the oil couplings on the radiator coolers.

Oil can blow back and collect in a place where there are no leaks.

 

Thanks guys. I guess I'll be crawling back under the Disco! I didn't think about the couplings. Thanks for the idea.