Blackxj51

1999 xj 4.0L 4wd

I have developed a decent oil leak, it drips down the bell housing and onto the transmission pan and then onto the transfer case and that flings it everywhere.
I checked my oil filter seal is dry, my oil filter adapter is dry, my distributor is dry, my oil pressure sending unit is dry, my valve cover is recently replaced and dry all around except for the back, now when I installed my new valve cover gasket i didn't use the new grommets i reused the old ones, but when i say the rear of the head isn't dry, it isn't fresh oil back there its like black crunchy oil so I don't believe that my valve cover is to blame, I recently installed a new oil pan gasket and its dry all around except in the back where it meets the bell housing, I didn't change RMS because its a rebuilt motor with 80k miles on it so i assumed it was still good. Is there anywhere else I should be checking, if it were a small drip I wouldn't be so concerned but it covers the whole transmission pan and theres a ton of small drops and drips everywhere and its driving me crazy

4WD4EVER

Although it takes more time initially, I would suggest cleaning the entire motor and trans. That way you're taking the guesswork out of it. You'll find it.

Blackxj51

After I changed my valve cover gasket I used three cans of that engine degreaser and it barely cut through anything so I wrapped up the distributor and fuse boxes and went in with a power washer and that helped alot but I cant get up in those deep cracks where the engine meets the bell housing underneath to get it as clean as the rest, is there something else I can try to get it cleaned up?

Also, I cant find my transmission breather vent so Im afraid to go to crazy with water for fear of getting some in the transmission

Jooman07

Hmm, well all those would be the main culprits of leaks of decent size. I have a decent size one that I thought was my oil filter adapter but turns out that the oil pan itself has a small hole rusted in it and that's where it's leaking. This leak has the same symptoms as yours. How long ago did you change the oil pan gasket and do you like where they salt roads on the winter?

4WD4EVER

Understood. Get a mirror to look for your vent. Then use a hard/firm bristle brush or even an old toothbrush to get some of the old build-up off in conjuction with a degreaser. Sometimes it just takes time + effort...

Many of the over-the-counter degreasing products simply don't work as well as we're led to believe also. The best one I've found is Purple Power, but, it's very harsh on aluminum and it will burn skin, etc. Normally I use Meguiar's Super Degreaser and Meguiar's All-Purpose Cleaner. They work exceptionally well, they're dilutable to the ratio you want/need and they will not harm metals, etc.

Blackxj51

You think it'd be best to remove the forward driveshaft to look for the vent? Is it on the direct middle of the Transmission?

jay_sco

sounds like a RMS to me. Was the rebuild done before you got it? If not there's really no way to know. Should have changed it anyway while you had the pan off, only a few more minutes and a couple more bucks.

4WD4EVER

Sorry for the delay chief, had a meeting.

Removing the driveshaft isn't going to help, so I wouldn't suggest creating more work for yourself. The vent is pretty far forward on the top of the AW4; almost to where it mates to the block.

Are you sure you've looked very closely at the mess of hoses, etc. that are typically routed down behind the head and firewall? I've seen people leave the breather hose just laying down in that area and it can be hard to spot in that case. Sometimes a mirror comes in handy in these cases.

At any rate, I guess I would just go with a plan "B" and clean any oil/crud as best I could to find the leak w/out worrying about getting water in the vent, but, that's not going to solve the vent hose issue; you'll still have to deal with that at some point.

Blackxj51

Yes it was done before I got it and I was debating doing the RMS but when it got down to it I couldn't get the pan all the way off and I was running out of day light so I snaked the new pan gasket onto the pan and rear bolted the pan back up. I tried disconnecting the steering parts to get the stabilizer out of the way so I could drop the pan but it wouldn't come apart

Blackxj51

I'll have to get my hand back behind the head and check for a loose hose because I looked all over and didn't see anything that looked like the pictures I found online of the vent hose, I was also gonna get some brake cleaner and spray around down there, to clean some of the oil off, you think that's ok or will it be to harsh on any seals it may get sprayed on

4WD4EVER

I don't believe it's going to hurt to spray some to clean up the area underneath to try and find where your oil leak is coming from. I believe I'd deal with the vent hose later. Best to find the oil leak first. Be sure and get the area way up between where the oil pan meets the block and bell housing. Let us know how it turns out.

Blackxj51

I mm going to stop on my way home and get some cleaning stuff, I'll post my findings, and try and take some pictures as well if I can, I appreciate all the help

4WD4EVER

You're quite welcome.

cruiser54

Really?




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

Blackxj51

I have checked valve covert gasket, oil pressure sending unit, oil filter adapter, and distributor gasket, those are are dry, but my transmission gasket had so much oil on it tonight after driving home that I could see it visibly dripping off of it