schadelh

1995 4.0 auto. The rear main seal appears to be leaking (changed the crank position sensor and it had some oil on it. bottom of belhousing/block is also oily looking). How soon do I need to change it? I add about 1/4 of a quart of oil each week. It kinda looks like it would be a PITA to change it, especially if the only issue is checking the oil more frequently. Any other problems it might cause down the line if i dont get it done soon?

xjcrazy

The problem with oil leaks on a 4,0 is that they all look like rear main seal leaks. Be sure to check the back of the valve cover, the oil filet adapter and the oil pan gasket. If all those check out then you can attack the rear main seal. The only way you are going to damage anything is if you let your jeep run out of oil killing your engine.

I just did the rear main seal and the oil gasket a few days ago. The hardest part fopr me was getting the pan out from the axle, that took me 2 frustrating days to get the pan out, and 1 hour to put it back together.

If you are going to do it be sure to check your engine mounts cause you can get to them real easy with the pan out the way.

cruiser54

Good advice here^^. The oil pressure sender and distributor base gasket can also mimmick a RMS leak. Always start at the top (valve cover gasket) and work your way down when checking for oil leaks. The fact that your CPS had oil on it indicates a valve cover leak at the rear.

schadelh

So as long as I make sure the oil is topped off, I shouldn't have to worry about damaging or fouling anything?

I might just leave the leaks alone until I have a driveway of my own to worry about (my property managers can suck oil). I recall a friend saying, "if it doesnt have dents, scratches, or leaks, it isnt really a jeep."

Thanks for the info

xjcrazy

The rear main seal sits in a channel at the back of the engine. The rubber gets bridle and the lip of the gasket starts to get little chips in it. The chips are what let the oil get through, Its a slow gradual death for the seal. Just watch the oil level. The longer you leave it the more it will leak, so sooner or later its going to force you to change it.

Bugsy

I usually break out the pressure washer and do the whole underside (especially good idea to do before you do any work under your rig). Give it some time to dry a little (give the pan area a wipe down so its all clean and clear). Run your engine run for a bit and give it a once around the block...then check for leaks. It should be fairly simple to see where its leaking from.
If it is your main rear seal, it isn't much to replace it...as xjcrazy says, the most difficult part is getting that pan dropped.
Myself, I would just change the pan gasket and rear main seal and be done with it.