I found the leak!

Despite everyone's great suggestions for finding the leak, I knew that oil leak was coming from area of rear main seal. I removed rear main seal housing (6 bolts facing rear of engine, 2 facing bottom) with seal still in it.

I was disappointed that the seal sealing surface looked and felt good...certainly not badly failed as I anticipated causing a sudden seal failiure. (see pic)

I spent some time really cleaning the whole assembly so I could thoroughly inspect it for another cause of failure. When it was cleaned, I was shocked at what I found...

The rear main seal housing appears to have suddenly failed in a manner that I've never seen. If I had to guess (and that's what I'm doing!), there was a small air bubble trapped inside the alloy comprising the seal housing that finally exploded badly cracking and distorting the housing at the time of failure. Note: the seal housing mates directly to the engine with no gasket...any imperfections will cause seal leakage, and certainly imperfections as large as the one I have had.

I can find no other reports of this happening to other 601/602/603 engines, but encourage any owners of these engines to thoroughly inspect this housing if replacing a suspected rear main seal failure.

Thank you all for your help!

Best,
Brad

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I recall the same gasket maker sealant as used for the oil pan is used between the seal carrier and block. It can't hurt.

Sixto
87 300D

There was no sealant on this, but I plan on using some on re-assembly.

Of note: while it's hard to tell in the picture, the seal carrier is way too deformed (there's actually a hole from front to back!) to re-use and will require replacement. While a sealant will help seal minor imperfections, this would be above and beyond it's call of duty .

Use the sealant specified in the FSM when re-installing. I wonder if a previous mechanic ever had this item removed...

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Dave
Boise, ID
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