CJ: 258 Oil Leak - need ideas

[Linus]

Good afternoon. I'm stumped on an oil leak problem. I have a 1985 CJ7 with a slightly modified 258. I have 31000 miles on a rebuild, and oil pressure varies between 30 and 60 PSI. For years it has had a very slow rear main seal leak. Something happend recently and the leak changed from a couple of drops per day to a major drizzle. I'm ending up with oil all over the entire back half of the engine, and the starter motor and front drive shaft are getting thoroughly soaked. I broke down and replaced the rear seal and it seemed to fix the problem, all was good, and I headed home with my significant other following close behind. On the freeway, about 10 minutes later, it started leaking again. Well leaking probably isn't the right word. She said that it looked like something blew, a big cloud of oil was produced, enough that she had to pull over and clean the oil off of the windshield of the car she was driving.

So, my question is -- what would cause a rear main seal to blow out almost explosively? I'm stumped and can't spend 6 hours replacing it every 20 miles. Any ideas would be greatly appreciated.

[Jeeperator]

Hows the pcv valve is it working properly ? Sure its not comin from the valve cover? Excessive blow by will cause crankcase pressure but never heard of blowing a rear main seal. Sure you put it in right?

[6spdYJ]

The AMC 6 cyl is also notorious for leaking at the valve cover right above the exhaust manifold.

[Lumpy Grits]

Had you changed the PCV before this started?
I have an '85 CJ-7 w/118K miles on the OEM 258 eng.
Started using Lucas engine oil stop leak and it works. My leaks(front & rear main)were just a few drops.
Did you buy your replacement seal from NAPA or one of those discount chains(Auto Zone, etc)?
X2 on check'n the valve cover. It will drain down and look like it's coming from the rear main
LG

[mrchips]

Did you start using a synthetic oil?

[Zoobi]

x3 on pcv and valve cover. Don't just make sure pcv is new but hooked up correctly. My 238 leaked also a while after rebuild. Replaced the rear main after checking everything else. Problem was gone. That was the first time I ever saw a defective seal. Too bad it turned out to be mine.

[Linus]

Thanks everyone

Thanks everyone for the suggestions, turns out there were multiple problems. I pulled the PCV valve out to check it, and it was clogged with a substance of similar color and consistency to cold cream. Sure enough, after pulling the head, I found a massively blown head gasket. Water was going into the oil and 4 of 6 cylindars. Odd that I didn't noitce it in the exhaust. There were other little indicators but I didn't think anything of them until it was too late. Oh well. I'll put the reconditioned head back on tomorrow, flush the oil a couple of times, and see what happens next.

[Lumpy Grits]

Make darn sure you RE-TORQUE the headbolts after about 500mi.
That is, you break loose the headbolt(1 at a time starting in the center of the head, BTW)about 1/2 turn and retorque to middle of the Ft-Lb. specs.
Use thread sealer(Permatex "black-tar" stuff)on ALL of the headbolt threads.
Use top of the line headgasket set from NAPA........
First oil & filter change after the head retorque.....
Good luck,
LG