Blacksj

Have a small oil leak that I thought was the rear mail seal. Change it and new oil pan gasket and still there. Oil drop comes right to bottom of bell housing on tranny. In center. Think maybe it might be coming from oil filter housing.
Idk any ideas. Also no I have a check engine light which I have to scan and see what from.

98XJ40K

Oil filter or valve cover gasket. The valve cover will drip down the back like that most of the time.

cruiser54

My standard advice on oil leaks. Perhaps you can relate.




　

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, 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 9-15-2012

DeftwillP

Modified tech?

cruiser54

Working on getting it moved to OEM.

CowboyXJ

I have the same issue, when I get around to it I'm doing the rear main, oil pan, and valve cover all at the same time.
How hard was the rear main seal. I found a two piece I was thinking of doing.

cruiser54

I wouldn't do the rear main until I was sure any leaks above were fixed. You might just find out that the rear main ain't leaking.

CowboyXJ

After fixing the things I've fixed on this XJ, I'm sure it'll need it. Just did a thermo change and I swear it was the OEM stat. Same as the water pump that went a week after the thermo.
Plus with my luck its one of those things where if I do it now then I won't have to later in a parking lot or side of road.

cruiser54

Rear main seal won't leave you stranded.

Radi

If the RMS isn't leaking, I vote to leave it alone. (didn't realize we were voting on it did you, lol) It isn't unusual for them to run 250K or more. Count the posts where they start to leak AFTER they've been replaced, lol.

CowboyXJ

XJ have about 330k. I was also thinking of doing CS and CR bearings while I was in there.

Blacksj

It wasn't that bad. But I would deff look to see if it could be coming from up top some where first. I watch a utube video about the rear main seal and it was very helpful.

cruiser54

Wise words from Radi.