I have noticed a oil leak that had started to show itself underneath my xj.... It's dripping from the bottom middle of the bell housing and also a very slow drip from the transmission pan.. I wiped the transmission pan a couple weeks ago and it's dripping oil already?? Would this be a bad rear main seal??

 

Yeah its a rear main seal and a common oil leak spot.

 

Cruiser should be along shortly with his handy progression of things to check before you assume it's the RMS. I had oil flowing to those spots as well and a valve cover gasket was the culprit.

 

Agreed, while it could be the RMS any oil leaking further up on the engine like the valve cover will end up down there.

Check the valve cover gasket, the adapter where the oil filter mounts, the oil filter itself for tightness, oil pan gasket, and even power steering leaks.

How many miles are on the engine?

 

I stole this from one of cruisers posts. 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

 

Steal it and use it as often as you like!! Better than telling some poor guy his RMS is leaking..........

 

Bookmarked. I have a similar oil link on my 95XJ. Thanks!

 

One leak source that became real serious on my 96 XJ was the distributor DRIVE shaft seal. Not the distributor mounting gasket. Tell tale sign is oil IN the distributor under the white rotating disc. This oil comes up the shaft and leave the distributor through two holes. Then it gets all over all of the stuff others already mentioned. Maybe those are real leaks too, but before spending time and $$$ on RMS etc, check inside your distributor. This happened twice to me. Once on a O'Reilly rebuilt unit not very old. Apparently between the top and bottom shaft bushings in the distributor there is some sort of O ring. Most are gone after 20 years. I solved the problem by getting a tight unit from a junk yard and taking the shaft out of the housing, cleaning it all up, and inserting a thin O ring in between the bushings before re-inserting the shaft. Had to whack the shaft into the housing with a mallet, but it has worked great and makes no leak.

 

The engine has 142k... I just replaced the head with a rebuilt one and replaced all gaskets... The leak was there before I installed the new valve cover gasket... Soo I think we can cross out valve cover gasket

 

Never hurts to look...or just replace the RMS, your driving the bus.

 

More time noggin pokin and less time typing.

 

So I realize this is an older post now, but i'm noticing oil drips whenever I park now and I found oil all over the bottom of my transmission and all along the sides of the oil pan. I was assuming it's the oil pan gasket... cylinder head was replaced about a year ago and valve cover gasket was replaced with it. Went with all fel pro gaskets, so I figured they should be good... is it possible it's failed after just a year? I see what appears to be a small amount of oil on the back of the valve cover but it doesn't look like it's enough to cause the mess I'm seeing underneath. Going to replace the oil drain plug this weekend if it stops raining (always try to go for the cheapest explanation first), but what should I be looking for to find the culprit? My diagnostic skills are lacking, but I'd like to avoid having to drop my oil pan if at all possible.

 

It's possible. Have you looked to verify or eliminate? Have you taken the aforementioned steps? You could clean it all off and look for it. Take the guesswork out.

 

See Post 6 for detailed instructions.

 

I changed the drain plug, wiped everything down real good and am waiting to see another spot on the driveway. It does look like there's some sort of moisture on the backmost bolt on the exhaust manifold, which I presume would come from the valve cover. Just seems weird that a fel pro gasket would blow in under 2 years... was installed by dealership so I'd have a hard time believing mechanic error. If I see any more drips I guess I'll go ahead and replace it.