I just rebuilt the stock run down 4.0L 6 cylinder engine in my 88 Jeep cherokee. The cylinder walls had to be bored .040 over due to the the egg shaped walls. Had a valve job and all parts boiled, professionally done of course. It had a small oil leak in the beginning and after only 5,000 miles on the new engine and 4 oil pan gaskets the small leak has turned into a very steady stream. It does not leak at idle even after running for almost an hour, but when driven down the road the new gasket will then start to stream. Now it runs at low oil pressure 20 - 30 psi. I have tried a new pan and several types of pan gaskets, I cant seem to stop this leak. It seems like it is on the back of the pan where it meets the rear bearing cap. What it causing all my unnecessary frustration?
The leak might not be from the pan gasket, but instead from the rear main seal. A pan gasket leak won’t pump oil out. But a rear main seal leak will.
Tester
Yep. Rear main seal. You can change it when you pull the pan down. It’s not too tricky working it around (the top half).
…but did you have any serious crank end play on this assembly? Is this a stick or auto?