Another thread about rear main seal issues

I replaced my clutch/flywheel in my 1994 ZJ a couple of weeks ago, and did the rear main seal at the same time, as I was getting a couple of drops out of it showing on the ground. Had no issues with oil leakage until last week, when I was noticing a puddle 4-6" across when I parked the Jeep. Seal went in facing the right way, cap was RTV'd, pan wasn't leaking after running it after the initial install. I also torqued the pan down to proper specs (7 lb/ft on all bolts). I did notice a score/scratch deep enough to catch my fingernail easily on the main cap when everything was pulled.

Due to the leak, I pulled everything back apart over the weekend to redo it. Same deal, used RTV where it should have been, torqued the pan correctly, used extra care to try to get the pan gasket to line up with the rear main cap. I ran it for 15 minutes or so once it was done to get the oil warmed up, and noticed 1-2 drops of oil underneath, which may have been residual. I then drive the Jeep 20 miles or so back to my apartment, and leave it overnight (parked on a slight downhill) only to come out to a puddle about 4" across the next morning. Drove it again the next day on a short trip, and had nothing leaking.

I'm at a loss with the whole thing- I figured if I had botched the install of either the seal or the pan gasket, it would leak right away. VC gasket was done a while ago, and it is damp around the back of the VC, but not blatantly leaking oil. Oil filter adapter housing and oil pressure sender don't show anything more than being slightly damp around the sides. Any thoughts?

Scrap it.


But seriously were either of the RMS's the dual lip or offset lip or what ever it is. Sometimes the crank gets a little worn down and the RMS doesn't make good contact. This other one moves the seal surface a little over to one side. Try that maybe? If that doesn't work I have a 4.0 you can have for cheapsies.

Both of them were the dual lip seals.

I really don't know if it's worth putting another motor in this thing, it's getting crusty.

squashman702 said:

Both of them were the dual lip seals.

I really don't know if it's worth putting another motor in this thing, it's getting crusty.

Click to expand...

My first solution still stands.

That's the direction this is heading.

Did you replace the VC gasket with cork...or rubber gasket?
How "damp" is the oil filter adapter?
Did you replace the oil pan gasket with a one piece or a four piece?

Reach up between the rear of the oil pan and the bell housing with a rag and clean the area between the two, wipe off all the oil and grime. Drive it for awhile, a day or a week. Then go back under there shine a light where you wiped it off. Could you be losing tranny/clutch fluid instead of oil?

If there isn't much oil, or even grimy, look elsewhere. The back of the block should be dry, the OFA should be dry. Clean off the whole engine...up, down, sides, bottom, front, rear. Drive it for awhile and check again.

Good luck, maybe you WON'T need a new engine.

Start here:




I'd be looking up ABOVE first, and VERIFYING the source of the oil leak YOURSELF.

Everybody, who doesn't own or have to pay for or perform your vehicle repairs, loves to poke their noggin UNDER the Jeep and come out bearing the false bad news that your RMS is leaking.

Many mechanics, friends, people on Jeep forums who can’t see your Jeep from where they’re at, and good old Uncle Bob seem to enjoy telling 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 or other source could produce the same symptoms. You don’t need to be a mechanic to figure this out. If you have good eyesight and a dim flashlight, you’re good to go on your own. Don't jump on the RMS/oil pan gasket bandwagon right off the bat.

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 any oil will run back to the RMS 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 02-26-2013

Oil pan gasket is a one piece Fel-pro. VC gasket looks to be the same, but I didn't replace that myself so I can't be 100% on that.

I cleaned everything pretty thoroughly when I did the clutch, but didn't get back under there for a few weeks. Need to degrease again I guess.

YES.