The valve cover gasket can leak a large amount of oil, and the rear is the most likely place for it to leak.

Try degreasing and cleaning the engine well. Let it dry, then go for a 10 mile ride.

Get some baby powder and sprinkle/blow it at the block everywhere you can.

The baby powder will stick to fresh oil leaking. See if it is at the top of the block or only near the RMS.

 

The valve cover gasket can leak a large amount of oil, and the rear is the most likely place for it to leak.

Decrease and clean the engine.l. Let it dry, then go for a 10 minute ride.

Get some baby powder and sprinkle/blow it at the block everywhere you can.

The baby powder will stick to fresh oil leaking. See if it is at the top of the block or only near the RMS.

This is you best advise.

 

Just let it run in the garage for about 30 minutes. I couldn't see any oil leaking anywhere. Makes me think even more that it is the valve cover, since you would think the RMS would leak pretty much all the time, even at idle, but the valve cover might not leak until higher RPMs.

 

Have you checked the torque on the valve cover bolts?

 

Haven't checked the valve cover bolts yet. There seems to be a lot of oil near the oil filter. The filter is installed correctly. A leak there could blow back and look like a rear main leak too. Has anyone seen this before?

 

Right, the rocker cover could leak and it would fall to the lowest point. The head gasket could for that matter, but it's unlikely. The split rear main can be problematic; gotta make sure the lip is facing correctly, and when you roll it in it can get scuffed on the groove side. AMC wants you to do the impossible...liquid soap on the groove side, engine oil on the main side, the dry the cap mating surfaces and apply rtv. Heck, even on the stand, crank out, upside down, it's tough!

You could go high-tech and get a some dye and a black light, which is what Daimler would suggest.

 

Would a RMS leak out of the bell housing only, or in the area between the oil pan and the bell housing? Right now I am only getting oil between the oil pan and bell housing, not out of the bell housing. It is hard to tell if fresh oil is coming from above that or not due to the 17 years of baked-on scum on the block. Definitely looks like fresh oil is coming out near the filter, but I can't tell if it is making its way all the way to the back of the oil pan...

 

A dye additive and black light is the recommended way if you have a lot of darkness and nooks/crannies. Kragen/NAPA, etc, carries dye and a cheap blacklite bulb or fresnel lens on a flashlight will illuminate the trail back to the source.

 

Check the valve cover. I replaced mine and it was still leaking. Turns out it was oil oozing out of the valve cover. Took care of that and no more oil puddle. Its easy to think its coming out of the rear main seal, I was convinced that was the issue. Until I found it.

 

I am experiencing the same problem with my cj. Just finished putting it back together today after installing new rms. Oil appears to be coming from the bellhousing. Very frustrated at this point...

 

I'm guessing that you're talking bout an 80 model 258. A very troublesome plastic cover was introduced around 81, which leaked badly. But as has been discussed, the lowest area of the engine/transmission will get the drip.

 

Yes sir. I'll change out the valve cover gasket as well. It's an oily mess as well.

 

Suedekustom, how long did you run it after changing out the RMS? When I originally posted I took it for about a 20 minute trip and brought it back in the garage, saw a few small runs of oil down the back of the oil pan. Cleaned it up and ran it for another 30 minutes or so, and got nothing else. It has been sitting in the garage since then and nothing has dripped out. I'm thinking the oil I saw the first time I ran it might have been some residual oil on the bellhousing/oil pan that I didn't get cleaned up, and when I got the engine hot it got thinner and ran down the oil pan. Seems like the rear main fixed my problem after that initial few runs of oil.

 

95turtle, after replacing the rms i ran engine for about 20 minutes or so in garage. After a while it slowed to just a minor drip while idling. Then I took it for a short drive, just a mile or two arounnd town. When i pulled back into the garage oil was running at a decent pace again. I ordered a valve cover gasket today hoping that will solve the issue. The old rms was hard and worn, when I installed the new upper piece into the block it did seem to skin off just a little bit of material on the outside edge once I got it about half way in. That could be the problem. I intend to sell the CJ next year and buy something newer, but I would like to solve this issue so I don't have to keep adding oil at an alarming rate when we take the kids out for a ride in it. After replacing rear axle bearings, all u joints, timing chain, and rms I am ready for a break from having oil and grease up to my elbows!

 

Jeeps like to mark their territory. In the old days, steam jenny the powertrain and then drive. You'd be able to see where it was coming from after a 20 min drive. Nowadays, the tech doesn't have that paid option so dye+blacklight is the method that will let you know right-away where it's coming from. When an apprentice AMC tech, I rolled a few upper rear mains into Eagles/Concords/Spirits only to scuff the upper edge, and, viola, leak. Over-torqued the plastic rocker cover..leak. But they, meaning any AMC/Jeep six from 81-87 was a oily mess due to the plastic rocker cover garbage, high-mileage leakes, etc. that made a definitive diagnosis challenging. The oil pan gasket has to be installed properly or it'll leak. The lip on the rear main HAS to face correctly or it'll leak like a sieve (serviced one that had the upper facing backward, lower forward). If you have a worn-out bottom-end (rare on the AMC sixes), it'll beat that new seal to leak again in 2k.

 

I've got a similar issue, with one change, I did the 4.0 head swap onto a 4.2 block, and at the same time did the RMS. I put it all back together and fired it up for the first time and it was leaking oil like crazy. I assumed at the time that it was the oil pan gasket since I used the 4 piece stock gasket and installed it myself and had a feeling that it just didnt seal well. So a few months later when I had some more time and an extra set of hands around, I dropped the oil pan again, installed a one piece gasket and retorqued. I never restarted it since I didn't have a battery and the jeep is not a dd. This past weekend I topped up the oil and was planning to start it, but when I went back out the next morning, there was a HUGE oil puddle, probably 1-2L of oil had leaked out. I was cover? Its not clear where the leak is coming from at this time, other than that its dripping off the bellhousing. Very similar to OP but I never started even had the vehicle running and had a huge leak. Please keep updating on how those of you with problems in this thread are doing with the solutions so far.

 

Fixed mine... It was the oil pan gasket, not the RMS. I didn't get it seated correctly around the rear main bearing cap. When I torqued the oil pan bolts the gasket tore and caused the leak. New oil pan gasket, no leak

 

Definite clean first. :thumbsup:
I also went through a lot of work finding my leak. It always seemed to spray a lot at highway speeds but nothing at idle. Changed dizzy, VCgasket, oil pan gasket. Timing chain cover gasket...till I finally changed the last thing(isn't it always) the Fuel pump. Turns out the gasket on it had blown out a piece and at high revs enough was thrown out and spread by the fan to confuse where it originated. Maybe yours is just a little less.