C5R UZR

After 16 months of slow work, I finally got my forged LS2 with LS3 top end fired up last weekend. The LS2 was used, stripped down, but inspected by the machine shop without issues and included most of the covers used in the build. Unfortunately, she's leaking a good bit of oil from the rear of the motor (into the bellhousing in particular), but it's wet all around the rear oil pan, starter, and into the front leaf spring area a bit. It's probably losing a quart in 10-15 minutes so it's not anything insignificant.

I thought maybe it was the oil pressure sensor dripping down from the top, but I looked at it and it appears dry. Since it's LS2, there is no Camshaft position sensor to leak up by the valley. The valley towers were individually plugged along with new o-rings and gasket.

I've pulled the intake manifold to see if it was leaking on the back of the valley down the bellhousing. It's pretty tough to see with the wiring harnesses and firewall clearances but even with an inspection mirror I'm not seeing any evidence of anything from above. Which only leads me to think it could be rear cover related - rear main, cover gasket, or insufficient sealant on the flexplate to crankshaft bolts (or I think less likely oil pan). I've also read a bit about the block porosity TSB - I reused the original LS2 rear cover with new gaskets. It's a pretty steady drip off the rear of the oil pan and through the weep hole between the pan and the bellhousing/inspection cover. I noticed that the rear main had some visible oil on it with the motor running, but I couldn't see it forming new drips. I plan on checking this again with some UV dye if I don't get any other thoughts. I feel like it's got to be more obvious, bigger than a minor seal issue, but it certainly is worse under pressure (motor running - in fact it sat for a few days with hardly a drop - probably just whatever had already come out); Oil pressure was good all the way around including good increase with RPM so I can't think it's a barbell/restrictor or gallery plug issue, but that was a thought I had as well. And I know the welch plug on the back of the crank can leak, but the crank came out of my LS1 and was fine before the build. It's an automatic, so I didn't mess it up with a pilot bearing or anything.

Anything else obvious to you? I'm trying to eliminate any further possibilities before I resort to pulling the rear cradle and torque tube to access the rear of the engine. And I'm worried about using the UV dye but not being able to see the source before it too goes everywhere.
Thanks!!

thundertruck

The location of the leak you describe sounds exactly like the leak that ZZ28ZZ and myself are both fighting. Here is a link to his post which has pictures of the leaking areas.

http://forums.corvetteforum.com/c5-t...-oil-leak.html

We both thought that it was our cam position sensor O-ring, but found that it was not going to be that easy. The rear engine cover seems to be a very common problem, and I have the cover/seal/gasket/bolts kit listed in the TSB on order for my 2000.

waddisme

http://forums.corvetteforum.com/auto...-my-block.html

Rear main seal for my LS2 with ~40k mi on motor.

C5R UZR

Just an update: I ran UV dye through the motor - man that stuff is pretty slick. Even without it though, with a 24" black light the oil luminesced pretty well. I'm pretty confident it is rear cover/seal related. I'll pull the torque tube and run the motor with the flywheel but without the bellhousing and confirm if it's rear main seal or a cover bolt issue. Through the inspection hole, I could see the majority of the oil coming down the far left side (driver) side of the rear cover (inside the bellhousing). So it's either coming from the top of the rear main seal or cover bolts above, as attached from a LS2 GTO. And then trickling down the side of the cover/curvature of the rear main seal outside casting lip. It's just nearly impossible to see any higher than the lower 1/3 of the crankshaft/flywheel.