Mystery oil leak

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Daniel Barrett

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I have a 2002 Yukon sle rwd with the 5.3. I have an oil leak that I can't track down. there's little drops of oil on the bottom of the bell housing, starter bolts and sometimes on the oil filter. it doesn't leaves any puddles on the driveway so I assume its only leaking when the engine is running. any ideas besides the rear main seal...I popped the inspection cover and it seems reasonably dry
 

Larryjb

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Go cheapest options first: Oil pressure sensor, valve cover gaskets, valley cover gasket (at the same time do the knock sensor gaskets).

Next level of expense: oil pan gasket.

Lastly rear main seal. In fact, it's probably the rear main cover rather than the rear main seal. These trucks use a rear cover in addition to the rear main seal. You can read over my thread here:
and

Sadly, mine was leaking exactly the same way yours was, and I had to do the rear main. I figure the rear main seal was, in fact, still good. However, the gasket on the rear cover had flattened out so much that the gasket was no longer sealing against the block. Look at posts 135 and 136 on the first link.

I'm about three years now with no leaks at the back.

Good luck!
 

Larryjb

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Oh yeah, forgot that one. Still wasn't my leak though in my case.
 

Sam Harris

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Fless

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I used my OE one but ran it around on some 100 grit sandpaper on my steel table saw top to make sure it was flat.
 

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