Oil leak from behind flywheel cover
 

Truck: 99 XJ 4x4, 2 door, 5 speed.

This is driving me nuts.

My oil pressure shot up to about 80 all of the sudden and the Jeep started running like hell. I replaced the oil pump, of course replacing the oil pan gasket at the same time. After idling for a little while with 60ish oil pressure I looked underneath and there was oil dripping right where the oil pan meets the transmission.

It looked like it was coming from the transmission side of the flywheel cover and it was dripping about 30 times a minute.

I dropped the pan again and replaced the rear main seal and put another new pan gasket on. The rear main that was in there looked like it had been done before so I figured I screwed up the pan gasket.

Started it up and thought it was good but after running for a while it's leaking in the same spot again, still about the same speed.

It doesn't leak when the engine is off. It seems to leak more when there is a load on the engine. It gets on my exhaust pipe and makes a smoke cloud when I come to stops at lights.

I'm going to replace the valve cover gasket tomorrow but I don't think that's it. I do see some leakage around it but all of that oil looks old and dirty wheras the stuff coming out underneath is as beautiful and clean as oil that has just been changed three times in a row should be.

What else could it be?

Sounds like the Rear Main Seal.

Edit: Sorry about that you should check the oil level in your transmission. It could be the Front Seal on the Transmission.

Sure does but the last one didn't leak and I did not mess with it when I changed the oil pump. Then, I put a brand new one in and the leak is the same ...

I have not had the truck long but unless they just put some really clean oil (not gear oil) in the trans, that's not it. Will check none the less.

I'd also think the trans would leak with the truck off or on. This leak only happens when it's running and gets worse with load.

Bump.

I am starting to wonder if this leak is coming from the oil filter housing and entering at the starter hole, then getting slung around by the flywheel and coming out where it is.

I found info on replacing the gasket behind the oil filter housing but it seems like that only pertains to older 4.0Ls. Mine is a 99. Anyone know if this is still done on the trucks with the L shaped housing?

did you putr the gasket on the pan or block when installing the new one

Are you certain you did not overtighten the oil pan bolts. Not to question your mechanical skills, but over tightening can split the gasket. Also check the valve cover gasket, it could be leaking down the back of the block. And the worst thing you want to hear, possibly the head gasket at the back of the block. One of the latter 2 might explain why it only drips while running and under a load.

we put it on the pan, and he just replaced the valve cover gasket yesterday... still leaking. definetly didn't wrench on the pan bolts hard at all.

i belive the gasket has to sit in a groove on the rear main cap it might have pushed out when you tightened it down get a light and look straight up between pan and dust cover see if you can see the gasket pushed out

The pan seems to go up under the dust cover, you know? Can't see the back of it. Was tucked up behind it and had to angle it out of there. Plus, that rubber piece with two 13MM bolts blocks the view of the area between the dust cover and the oil pan.

What a PITA.

pretty sure gasket has to go on block you got a manual for it ?

From my other thread:
When you say stick, I assume you mean with RTV? The first time I did not use any RTV. The second time I put RTV on both the oil pan and the bottom of the block. Then I stuck bolts through the pan to hold the gasket in place and raised it up to the block.

Not sure what you are saying. The gasket goes against the block, yes. You just can't see anything between the oil pan and dust cover for the flywheel because of the rubber thing between the two 13MM bolts and the pan actually goes behind the dust cover a little anyway.