is there a way for me to verify that it's definitely a rear main seal?

I`d crawl under there with some rags and a can of brake cleaner and blast everything clean and dry and then start it up and watch closely.. But watch REAL closely as I was certain my rear main seal was leaking even after laying under there and watching..The path the oil was taking down the side of the black engine block and along that hidden ledge and then around the crack between the engine/transmission made it look like that`s where the leak was at...Only after the leak got worse and the oil flow was to much to for that little ledge to handle and it started coming out in the front did I discover the real leak source...BUT that was just my experience..The only reason I jumped in to suggest this was because you mentioned oil leaking on to your exhaust which seems a bit to far off to the side for a rear main seal leak.. Just give it a good clean and dry and see what happens.. Either place isn`t an expensive or overly difficult repair if you have the tools and take your time

i believe mine is doing the same thing. when driving the wind can blow the oil back to make you think its the rear main. im sure the oil filter housing gaskets are cheaper, and easier to install. i am starting there.

I have the same issue, more or less...I am leaking out the main, as well as the oil fillter adapter. It is going to cost me $520 to have my local Jeep mechanic do the filter adapter gasket, the rear main, and replace all the screwed up PCV breather crap that crumbled to dust a few months back. Totally worth it to have it done right by someone who knows WTF they are doing.
I could probably do it myself (and so could you) but I am more paranoid about killing ny XJ than I am broke, so to the shop she will go.

I have 178K on my 1990...and I plan on at the least putting 300k more before I give up on her...and just so you know, she has leaked oil most of the 14 years I have owned her. Just keep adding oil if you need to for a time. "My Jeep doesn't leak oil...It marks it's territory!"

i like that last one haha

i'm beginning to think I want to have it done professionally as well. I don't have the tools or the knowledge to really be doing this on my own. I think i'll take it to get looked at.

As for now, i guess she'll just keep blowing the little bit of smoke here and there. It's not a constant smoke, and it doesn't always happen...i usually have to have it running for at least an hour with a decent load on the engine to heat it up before it'll even start.

That sounds like mine...I don't smoke so much when rolling down the road, but when she comes to a stop...it looks like a james bond smoke screen, lol. probably a bad main seal being the worst culprit for both of us. My mech said the oil filler was "seeping" but that was the least of the leak problems.

On the bright side, with enough patience and some proper maintenance, once you get the seals squared away, these engines are fairly bullet proof.

An external oil leak has nothing to do with the oiling system to the bearings and such unless it leaks out enough to be too low for your sump to pick up. You are safe to run it leaking. For engines with a few miles on them that seem to go through the rear main seal, ive heard that by replacing just the far rear main bearing (providing the crank is in good shape) will hold the crank in place enough not to wear it out so fast.

I'm getting ready to do this on my wifes 88 xj, she has 248000 miles and its been leaking oil sinse the day we gat it 8 years ago. I replaced the valve cvr gasket with the one everyone on here recomendes and bought the same type of gasket for the oil pan. I still need to purchase the rear main seal at 16.99 at autozone but i'd rather do it myself than give it to some mechanic who will somehow find something else wrong and rape you.Just remember to jack the jeep up from the frame rails to let the front axle doop down farther and id really shouldn't be that bad. Good luck with yours and let us know how you make out.

You never junk a 4.0. They will run forever.. my first car was a 92 with 270k on it and it ran like a champ. I have the same symptoms you do on my 90 that i just picked up. I'm gonna check everything else before I go into the rear seal even though i'm quite positive that's my problem. good luck

I know this may seem like something thats kind of hard, but its not that hard. and i guess idk what you have for a tool selection, but you should only need a few pretty standard metric sizes, sockets and extensions, and a LOT of pb blaster. I can tell you one thing tho, if you do this yourself, first, you'll save a bunch of money, and second, you'll get the exp. of working on it. I'd say im only moderately to intermediately mechanically inclined, and me and my friend ripped the oil pan off his wrangler, new gasket, and put it back on in about an hour and a half, and got a little dirty but ive been worse. Me and him are both 19. I have to do this on my jeep too, im gonna wait a few thousand miles so i can just change the oil while im there. Oh yea and whoever said the thing about the high performance mopar oil pump, GREAT idea, im def keeping that in mind.

ok i got oil coming out the dipstick some i think it blows the dipstick up and my right passenger side lower control arm has oil on it or is the upper one, sounds like a rear main to anyone?

if it is coming out the dip stick and you can see it,you have a ring problem and a pcv problem,dipsticks should not be blowen up from there tube,no that does not sound like a rear main seal leak.
I would do a compression check.

bad power booster do this?

like jamie said if your not lifted jack it up and support it so the axle hangs down this makes gettin the pan out alot easier just remember to be careful when manuvering it outta there so ya dont bang the pump around (BTW the pump doesnt need to be removed) then when thats outta the way unbolt the rear bearing cap and be sure to make note of how it came out (front,rear,left,right) and the seal is a 2 piece which the bottom will come off easily enough its the upper half that you will need to force out( a thing punch helps here) the seal has a metal wire in it and you wanna tap on that to push the seal out and be VERY careful not to scratch or hit the crank shaft then bolt it all back together and to torque spec besure to clean any old gasket off of the mounting surface between the pan and the block and it should be good to go

5-6Hrs and a bit of patience and you should be good to go

i did mine when it was around 0*c and that sucked so this time of year should be easy

good luck