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Rear main seal

B

benni302

NAXJA Forum User
Location
bonaire, ga
Hello everyone, i am new to the forum and hope someone may have some suggestions for a problem. My wife bought me an 88 xj for christmas to toy around with, it is bone stock with the original 4.0 and 140,000 mi. It runs strong and everything on it works, but it appears the rear main seal is leaking(at least thats what it looks like). Has anyone had to replace theirs and how difficult is it? My wife only gave $900 for it and i just want to make sure its worth the trouble. Thanks in advance.
 
Here's another writeup with pictures. My rear main has a slow drip as well, so I'll be tackling this one myself in the very near future. Looks easy enough.

http://www.go.jeep-xj.info/HowtoRearMain.htm

HowtoRearMain.htm_txt_RearMain%20005.gif
 
There are ton's of main seal threads here and on other forums. Spend some time searching. Make sure you read everything twice BEFORE you remove anything.

Doing my '88 took a few hours. Most of it was cleaning the old gasket from the oil pan and block.

Get ready to get dirty. Very dirty.
 
thanks for the input, i didnt realize there were so many posts on the rear main seal. i'm not even 100% sure thats the problem, but i started it up last night and let it run for approx 15 mins and after letting it sit for about 15 mins there was probably 1/2 qt on the piece of cardboard i put down. any other thoughts on what could be leaking? i just got it last week and havent really had time to clean it up good(engine) and trace it down.
 
If you're sure it's engine oil and not trans fluid, start with the good cleaning. It could also be the back end of the valve cover gasket.
 
It is also possible it is just the oil pan gasket has gotten pushed out in the rear while someone put the oil pan on - had this happen after doing a rear main seal and it leaked REAL bad, exactly like you describe. Easiest way to check is to loosen but NOT REMOVE the pan bolts and tighten them up in the proper sequence while holding the gasket back in place.

If it is the cork gasket on the pan, take the whole thing off and get the rubber one - could be the cork is dead and the rubber one isn't much more expensive.
 
Easiest way to check the valve cover is to feel if the back of the block is wet. Also check the oil filter adapter which is the aluminum right angled piece that the oil filter screws on to. You'll typically see the pass side of the engine wet with oil, but it does tend to run down the back. The o-rings in there are a common problem. The oring kit is around $5 from the dealer and fairly easy to swap out.
 
if you do replace the rear main you might as well run to the dealer and get the o-rings for the fliter housing as well and change them out while you are dirty and on your back. i changed my main out a while ago and got full oil pressure back and blew out the o-rings. something to think about with an older rig
 
Reading back, I see no one mentioned the crankcase vent. If that's plugged up you'll get oil in the air filter and tend to exacerbate existing leakings. Pull off the plastic line that comes out the rear top of the valve cover and flush it with carb cleaner.
 
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