90 Wrangler YJ needs Rear Main Seal

First thing you will hear from most others in this group is that your problem is more likely the valve cover gasket. (Maybe you have already heard it)

Mine (80 CJ) was a 2 piece seal... not that hard to replace. You must remove the oil pan. The passenger side motor mount on my CJ had to be removed.

JimG said it: FWIW, I found the bolts for the valve cover on my '89 YJ 4.2 finger tight. Torqued them and my rear main seal leak was gone. Joe

I've done this 3 or 4 times, the folks at AutoZone kept giving me the double-lip seal and it kept leaking. My '88 has a single-lip 2-piece seal, though visually I simply can't tell the difference between the double and single lip versions (other than the color of the rubber). You're looking for Fel-Pro gasket part # BS13879 (I'm almost positive, if it's not that it's something close.) The biggest trouble you'll have is reinstalling the top half - the instructions say to use liquid soap to lube it up, but I ended up putting a coat of lithium grease on the thing, then dunking it in the motor oil I'd drained out of the pan. Use a screwdriver to compress the side of the top seal as you push it in with your fingers to keep from shredding the outside of it on the block.. If you've never done this before it's good to have a backup seal just in case you do shred it. Take your time and wear eye protection, oil will drip off your crankshaft and into your eyes. The lower half of the seal just Other than that it's a very straightforward operation, all you have to do is unbolt your starter (I just let the thing hang on a piece of rope so I wouldn't have to undo all the wiring to it) and then undo 20 or 30 7/16" bolts around the oil pan to get at the thing.

The obligatory Jeep group statement on leaking 258's: Check Your Valve Cover Gasket. 99% of the time, due partially to the downward slant of the engine, oil will leak out of the back of your valve cover, run down the engine, and fall on the ground between engine and tranny, causing you to believe your RMS is bad. Stuff a rag between the back of your block and your firewall. If it has oil on it, you've found a leak. It might not be a bad idea just to replace the VC gasket first, since the part costs no more than $5 and is simple to replace. This can also happen with your valve cover (PCV) grommets getting old and dry - oil can leak out of them and down the back of your block. That being said, if it *is* your rear main seal, check your timing chain while you've got the oil pan out. If it moves more than an inch or so with just your finger, you may as well replace it while you're in there.

If you run > First thing you will hear from most others in this group is that your

Hey Jeff, Another donor to both the Jeep and BMW boards huh? Joe C '89 YJ 4.2 5spd '02 325CI 5spd

I just did the one in my '87. It was the rear main. I replaced the valve cover gasket too, but the rear main was the culprit in my leak. It was hard and brittle, and I had to loosen all the main caps to get the upper part to budge. I've done lots of rear mains, this one was easy. Get the good Felpro gaskets, and save yourself some trouble. Be sure to use plenty of lube or lithium grease on the new seal as you install it, and, the lip goes toward the front of the engine.

Spdloader

Thanks all for your help so far. I have replaced the Valve Cover Gasket as suggested before posting this message and have gotten the thing pretty much narrowed down to the rear main seal. Unless it can leak from somewhere else in back and make a few of us think its the Rear Main.

Micah, thanks for all the info you put in and you stated that it is a

2 piece seal? Not a one piece? As I stated I have the 90 Wrangler YJ with the 258 4.2L engine in it and I was talking to a couple auto parts shops and they kept asking me if it had the 1 or 2 piece seal. I guess I got confused because to me with that year and engine it should be pretty straightforward which one it would be. So I need to look for the FEL-BS13879 part by Fel-Pro. I did a quick search and that states 2 piece Rear Main Seal application for the AMC/ International/Jeep 196-258 L6 engines.

Now would you have any good instructions or reference to any on the net to print out while I tackle this fun project. I'm a computer person that is just getting into this jeep and engine stuff but know it will save me lots of money if I can do some basic or the easier stuff than going to the shop all the time.

Thanks. snipped-for-privacy@yahoo.com

FWIW: My parts manual for the '90 4.2L clearly shows a 2 piece rear main.

I know every> Thanks all for your help so far. I have replaced the Valve Cover

Thanks for the post RoyJ, I am pretty confident that its the Rear Main that is leaking. Since there is no oil towards the top of my engine or even the backup of the engine and the firewall. Thanks for the information from your manual showing that it is indeed a 2 piece rear main.

Now does anyone have a good document to follow to replace this seal? Thanks again.

Remember the rope seals? There was a Chinese finger toy type of tool you could use to try to drag the new one into place. Leave just the right amount of rope sticking out, and the cap would compress the seal so it would maybe not leak for a while. Cut off too much or too little and you had to do the job over. I like the type where you have to take the flywheel off.

Earle

If you don't use the clean rag test for the valve cover, you could be doing a whole bunch of work for nothing.

Is your valve cover bone dry all around? If it leaks up front, well....

The leak down the back will not be visible from up top or down under. None will get on the firewall either.

Just my $0.02,

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail > Thanks for the post RoyJ, I am pretty confident that its the Rear Main

FWIW, after tightening the valve cover gasket, it takes quite a while for the oil to stop dripping on the garage floor! Joe