Baffling Oil Leak

I have a 2010 Yukon Denali with an oil leak I can't pinpoint. Seems to be pooling and running down the sides of the bell housing. Just put a new valve cover and both gaskets, new vlom, oil pressure sender, oil coolers lines and oil pan gaskets in it. Cleaned it all up and found the same steady stream down the driver's side of the tranny. Where else could it be coming from?

Oil cooler adapter gasket possibly. Or, you have a rear main housing gasket that is compressed and leaking. The rear of the engine has a cover that holds the rear main seal, as well as provides a block off to the high pressure oil valleys in the block. The gasket material gets stiff, then weeps. I put mine off until I got sick of changing the cardboard diaper under the truck......you get to pull the trans to do it. But, leak free is a nice change.

B-train said:

Oil cooler adapter gasket possibly. Or, you have a rear main housing gasket that is compressed and leaking. The rear of the engine has a cover that holds the rear main seal, as well as provides a block off to the high pressure oil valleys in the block. The gasket material gets stiff, then weeps. I put mine off until I got sick of changing the cardboard diaper under the truck......you get to pull the trans to do it. But, leak free is a nice change.

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Oil cooler gasket is good, it's running down from higher up. That's where I get confused. Just pulled the intake and poked around and couldn't find any oil around the usual suspects. Wouldn't think oil would get pushed upward and out the top of the bell housing would you?

Rear main seal, unfortunately.

Put some dye in the oil, take it for a spin, then crawl under with a black SUV light. I struggled to find mine. Started replacing everything from the top, down: valley cover gasket, camshaft sensor, confirmed the oil pressure sensor wasn't leaking (and I had already replaced the oil pan gasket.) I'm a Gen III BTW.

It wasn't until I added the dye, and even then it was hard to see.

Going through the same thing. I can see where the oil is running down from top to the bottom of the bell. Pools up enough to run down both sides. About a quart every few or four days.

BH86 said:

Going through the same thing. I can see where the oil is running down from top to the bottom of the bell. Pools up enough to run down both sides. About a quart every few or four days.

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I remember mine just seeped a little bit. When I changed my oil, the starter bolts always had oil dripping from them (why I replaced the oil pan initially.) Also the little oil pans at the rear

Then all of the sudden, it started dripping a lot of oil, like it was leaving a puddle on my driveway.

I found a photo I took on my old laptop. I just emailed it to myself. I will post it. Maybe it will help you where to check...hang tight.

Edit: here it is. I believe I had to rotate the flexplate so I could shine my light through the flexplate holes. It still didn't really come out clear on the photo...

strutaeng said:

I remember mine just seeped a little bit. When I changed my oil, the starter always had oil dripping from them (why I replaced the oil pan initially.)

Then all of the sudden, it started dripping a lot of oil, like it was leaving a puddle on my driveway.

I found a photo I took on my old laptop. I just emailed it to myself. I will post it. Maybe it will help you where to check...hang tight.

Edit: here it is. I believe I had to rotate the flexplate so I could shine my light through the flexplate holes. It it didn't really come out clear on the photo...

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I'm probably just going to replace it anyway. Just fishing for other explanations, but I've already been through everything else. Just baffles me cause of where it's running down from is all.

I found more photos after I had removed the transmission and flexplate...

To clarify, I called it the "rear main seal" (RMS.) I guess it's technically the crankshaft flange seal. The RMS cover has a metal-clad gasket, which usually is not the culprit. I refer to both gaskets/seals as "RMS" since the kit has both pieces.

Dangit probably my leak as well.. and my oil pan was looking extra oily last time I looked under there..

Rear main seal and/or its cover
https://www.tahoeyukonforum.com/threads/is-it-the-rear-main.109967/#post-1312967