Looking for Help - Source of Oil Leak

[SFJ_RS6]

I've got the dreaded "where's that oil leaking from?" situation...

Has anybody seen oil on their engine/transmission in the location shown in the photos and figured out where it's coming from?

When the engine was in the car, the bottom of the RH (passenger) differential case was dripping oil, and it appeared to be engine oil. My first thought was that the rear main seal or rear main seal flange was leaking. But with the engine out and the RH turbo removed, it looks like the oil may be coming down from above instead.

I think I can rule out a couple of sources - the valve cover gaskets (replaced in 2012 ~20K mi. ago) don't seem to be leaking since I don't see oil on the outside or back of the RH cylinder head. Also, the seam where the head gasket lives between the bottom of the head and top of the block is dry.

I assume our BCY engines have a valley pan gasket, which could be the source? As you see in the pictures, the oil runs down the RH side of the transmission bell housing, just behind where the transmission meets the engine. (No oil running down on the LH side.)

Before I do further work, like removing the intake manifold and/or separating the transmission, I'd appreciate any input to make sure I'm working where I'm most likely to find the source of the leak.

For some reason my photos uploaded rotated 90 degrees counterclockwise - sorry about that! :)

Thanks for your help!
Steve

https://www.rs6.com/attachment.php?attachmentid=19158&stc=1https://www.rs6.com/attachment.php?attachmentid=19159&stc=1https://www.rs6.com/attachment.php?attachmentid=19160&stc=1https://www.rs6.com/attachment.php?attachmentid=19161&stc=1

[lswing]

Have you replaced the plastic oil cooler pipe? Bufkin makes a metal one. You did say passenger side leak right? Search in google for more info on it, "site:rs6.com bufkin oil cooler pipe"

[SFJ_RS6]

Thanks lswing. Yes - I replaced the plastic oil cooler pipe with a Bufkin aluminum pipe when I had the engine out a few years ago.

The leak is on the passenger side. it's further back from the oil cooler assembly, and it runs down the transmission bell housing onto the RH differential housing.

As a next step, I'm planning to take off the water pipe and air tubes under the MAFS at the back of the engine so I can get a better view at the top rear of the engine.

Has anybody else had this and tried to troubleshoot it?

[bethridg]

Half moon seal and/or cam tensioner gasket. Should be easy to spot with the motor out but it's been a long time since I had a motor with all the emissions nonsense in the way.