What's up guys, I've got an 89 Cherokee with a 4.0, auto, 4wd. Rear main seal has a pretty decent leak at this point but I was advised that with 260k miles at this point, that the cam probably has play And will just chew up the new seal and leak worse than before. Does anybody have say in this? Thanks guys, -Paul

 

I'd be looking up above first, and VERIFYING the source of the oil leak yourself. Many mechanics and friends love to tell you it’s the rear main seal. Has a catastrophic ring to it, doesn’t it? A simple leak at the back of the valve cover could produce the same symptoms. Don't jump on the RMS/oil pan gasket bandwagon just yet.

Almost any oil leak on your 4.0 is gonna drip from the RMS area for two simple reasons.
First off, the engine sits nose-up and oil will run back to that area. Secondly, the RMS area is also the lowest point on the engine. Simple physics and the old plumber's adage apply here. "$hit flows downhill".

Valve cover gasket, oil pressure sending unit, oil filter adapter seals and distributor gasket, in that order, have to be eliminated as possibilities first.
Revised 5-19-2012

 

Cam don't touch the rear main seal!!

 

I'm thinking the advice you're getting is not good. Using my previous post, you can figure it out for yourself. How in the world can someone know how much play is in your cam without disassembling the engine anyway? Not that it affects the RMS anyway........

 

I'm with Crusier54. Clean it up and find for sure where the leak is.
If it is the rear main, I think a new fresh soft pliable seal would seal better than an old hard dried up one even if there is some play in the crank.

 

260,000 put a valve cover gasket on it any way while you there

 

We don't know it's a RMS. Everybody who doesn't own your vehicle likes to say it's the rear main for exactly the reasons in my post. Is it a macho thing or something?

 

step one finding oil leaks start at the highest point oil runs down just as Cruiser suggesting

 

Yeah. And you don't need cousin Benny or Uncle Clem telling you what it is. You are now well equipped to diagnose it on your own. If you have any questions, post them up. We'll help you.

 

LOL

 

Don't tell me you have an Uncle Clem!!!

 

Lol. Let me put it this way- if I cruise down the highway for about an hour, my rear window will have a light coating of oil on it. That's how bad the leak is, because it's running under the Truck and up the back window (only on highway runs). kind of hard to believe a valve cover gasket could be leaking that bad, but i guess it does make sense to start high and work my way down with finding the leak. Thanks guys!

 

Oil filter adapter is under pressure and it can leak like a sieve.

You just need to start from the top and diagnose it properly.

 

Nope had a Uncle Jeb though....

 

Granted I put in new motor, but I had leak that LOOKED like RMS, but distributor, valve cover, and oil pan had all loosened up. Now my oil filter is leaking, but thats another story. Check the rest first, you'd be surprised how much oil you can lose!