RMS replacement

This is my first post so sorry in advance if there's a thread about this already in the forums...

Anyhow, I have a 92xj 4.0 with a major, MAJOR rear seal leak. I'm talking about dropping a quart a day. Its been leaking for 2 years (only dime size drips over night) and after a oil change this summer, the rear seal went from "no big deal" to must-do, demand service. I have talked to co-workers and they said I would need to pull off the transmission to gain access (I work at a decent size bodyshop), but I have also talked to a few people who say I can just drop the exhaust, starter and remove the oil pan to get at the 2 peice seal.

Any advice or tips would be cool.

Also, I replaced the oil filter adapter o-rings a year ago as well as the valve cover gasket. In other words, I'm very sure its the RMS.

Also, I am going to drop the oil pan to clean it out and check the oil pickup.

Does anyone have a link or any first hand experience with a rear main seal on a 4.0?

Yea, search "rear main seal". Also you do NOT drop the tranny. The seal is two piece from the factory. Should take about 4 hours to do. Not hard just sloppy.

Here are a couple links that should cover it all:
http://www.myjeeprocks.com/features/index.php/Rear_Main_Seal_Removal_and_Installation
http://www.jeepin.com/features/rearmain

Also, make sure you get the one piece oil pan gasket from the later model cherokees. I got mine from NAPA, '96 and newer I believe.

Good luck! I did mine for the first time recently and taking my time and few trips to the parts store took me 8 hrs. After having done it now and having all the right tools I think four hours is realistic.

smcdonaldaz said:

Here are a couple links that should cover it all:
http://www.myjeeprocks.com/features/index.php/Rear_Main_Seal_Removal_and_Installation
http://www.jeepin.com/features/rearmain

Also, make sure you get the one piece oil pan gasket from the later model cherokees. I got mine from NAPA, '96 and newer I believe.

Good luck! I did mine for the first time recently and taking my time and few trips to the parts store took me 8 hrs. After having done it now and having all the right tools I think four hours is realistic.

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Thanks for that. I searched and found another step-by-step with pictures but the one you posted is way better. I shouldnt have a problem with it, a lift helps .

yeah, a lift will lift will help big-time. Mine took me quite a while to do the first time, but it was also the first time I had been in an engine. Now that I have alot more experience wrenching I think that 4-6hrs is pretty realistic, depending on how stuck on the old gasket is, how much sludge there is in the bottom of the oil pan (mine had around a quart of nasty hard sludge..ouch).

Feel around the back of the valve cover first, it impersonates a rear seal leak better than the rear seal LOL, they do tend to leak from there.

clunk said:

yeah, a lift will lift will help big-time. Mine took me quite a while to do the first time, but it was also the first time I had been in an engine. Now that I have alot more experience wrenching I think that 4-6hrs is pretty realistic, depending on how stuck on the old gasket is, how much sludge there is in the bottom of the oil pan (mine had around a quart of nasty hard sludge..ouch).

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Thats one big reason I am not looking forward to this. For about 3 years, when checking oil level, I notice at the bottom a small amount of what looks like brown mud. Its just condensation-in-sludge I think. I'll tell you this, when I change it the seal, I'll be wearing old pants and a crappy shirt! I changed rear seals on big block chevy/ford and small blocks before, but thats a whole lotta bolts on the pan :shocked: !

yeah, it's a pretty messy job, but if you have a lift/hoist that'll make it alot easier.

I'd also recommend checking everything you can while your under there, because it probably isn't a job you'll want to do more than once. If you have the money, I'd replace the oil pump while you are in there (unless your rig has low mileage). The oil pump is known to go forever, but a replacement won't cost you much and it'll give you a bit of piece of mind. Also get some plastigauge and check main bearing clearances, have a look at the timing chain etc.

The sludge will probably scare the crap out of you. I did the RMS job around 2 weeks after I bought the jeep, so I was pretty unfamiliar with it and also didn't know what ANY of the past maintenance was. I scraped around a solid inch of hard, crystally sludge off the bottom of the pan, but luckily didn't find any metal in there. At that point I decided it was a good idea to pop the main bearing caps off and check them for wear. Luckily they were all well within spec.

After you clean all the sludge out, you might want to do a few more quick oil changes with cheap filters and thin oil (the cheapest you can find since you'll be changing it within 100 miles or so anyways), perhaps with some kind of oil flush like a quart of ATF+ or MMO in the crankcase and let it idle or with a little VERY LIGHT driving (around the block a few times). Change the oil when hot and hope that you can get as much of the remaining sludge out of the block as possible.
I suggested doing the engine cleaning after the RMS change since you don't want to put any cleaners in there with the existing sludge..it could stir them all up, causing some blocked oil passages or a blocked oil pickup screen..both of which could kill your engine.

clunk said:

After you clean all the sludge out, you might want to do a few more quick oil changes with cheap filters and thin oil (the cheapest you can find since you'll be changing it within 100 miles or so anyways), perhaps with some kind of oil flush like a quart of ATF+ or MMO in the crankcase and let it idle or with a little VERY LIGHT driving (around the block a few times). Change the oil when hot and hope that you can get as much of the remaining sludge out of the block as possible.
I suggested doing the engine cleaning after the RMS change since you don't want to put any cleaners in there with the existing sludge..it could stir them all up, causing some blocked oil passages or a blocked oil pickup screen..both of which could kill your engine.

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Don't get me started on the danger of flushing a engine thats really dirty. In november I was helping a friend get his Buick Regal 3.8 w/120,000 miles ready for winter. I serviced the ignition, battery, brakes and change all fluids except power steering. I checked the oil, it smelled like plastic, not good. Drained it, it looked like any other oil other than the smell. I flushed the engine with bulk oil/gold eagle flush, napa gold filter. When I drained the oil, I am not kidding, it looked like a fine "House of Kolor" pearl paint there was so many fine metal particles!! To make a already long story short (too late), the engine was so dirty the flush clogged the pickup screen so it killed the oil pressure. (It had that same kinda knock that happened when you rammed a car too much in GTA!!) A pan drop should have kept the engine from failing, but I kinda doubt it.

Used mid-mileage engine: 700$
Labor: 600$
Parts: 300$
Not changing your oil since april 2005 and 23k miles: Priceless (or around 1700 dollars :laugh3

RichP said:

Feel around the back of the valve cover first, it impersonates a rear seal leak better than the rear seal LOL, they do tend to leak from there.

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Its not the valve cover, I replaced that a while back. Also, I did check the valve cover near the firewall and its dry. But I know what your talking about, I had to replace it when I thought the real seal was getting worse, only to find it was a 20 min fix.