Rear Main Seal Replacement - Lessons Learned

This is a short list of items that I didn't read about in any of the writeups. Most of them were non-issues, but worth mentioning

• Many of the oil pan bolts have studs protruding from them, make sure you have a deep socket. Many writeups suggest replacing with stainless. Good luck finding these special bolts in SS.
• The bearing brace on late model XJ's is held to the bearing cap bolts via studs that protrude from the bearing cap bolts. Make sure your bearing cap socket is a deep socket.
• Most writeups "can't remember" size of bearing cap bolts. 3/4" is too small. 13/16th fit the best, but felt a tad sloppy IMO. 20mm and 21mm sockets don't fit. I used 13/16ths.
• If you have a factory front skid, allocate time to remove this as well. You may be able to work around it, but it blocks access to many oil pan bolts, and you risk smacking your forehead on it.
• Brass punches bend really easily
• It's pointless trying to keep the oil pan gasket lined up with the oil pan while reinstalling. You can use zip ties to keep the gasket in place.
• '99+ XJ's have an oil pan support bracket that gets int he way of the two large oil pan bolts near the bell-housing. You should be able to jam your socket on these bolts, bending the rubber out of the way. The rubber may crack, requiring a new support bracket.
• One of the large bell housing bolts that holds on the inspection plate will hit the exhaust downpipe before the nut can be removed. Be prepared to bend the inspection plate with pliers to facilitate removal

Some helpful info but it should be noted that these issues don't apply to all xj's. I've changed the RMS in my 92 and 93 and didn't have any of the problems you say you had. Yes a brass punch can bend easily but that also means it being softer won't gouge the block when tapping out the old seal. Not all xj's have the bearing brace going along the bottom or the pan support bracket on the back.

Sorry, I have learned my lesson on doing rear main seals..

Pull the motor, put it on a stand.. Might sound hard.. but it gives you a chance to replace alot of things within minutes! I'm not fond of laying on my azz having chit fall in my face. even with a creeper..

nw-xj-scott said:

Sorry, I have learned my lesson on doing rear main seals..

Pull the motor, put it on a stand.. Might sound hard.. but it gives you a chance to replace alot of things within minutes! I'm not fond of laying on my azz having chit fall in my face. even with a creeper..

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I waited until my motor was out to do my rear main, I think it would have been a living nightmare to do it in the jeep. The problem is made worse when you've hot a stud girdle that has to be removed and then re-torqued. Getting a long torque wrench towards the front, PITA!!

And it's really not that hard to get the motor out if you have a hoist, if you compare it with doing the rear main in the jeep it's way easier than an in jeep rear main replacement.

once you do one or two rear mains,you can grab the tools you already know you`ll need,air hose included,jack the jeep up by whatever means you use,get underneath and go to work.

you will probably only have to come back out when it`s time to clean the gasket and wash the oil pan out.

apply sealer to pan,get back under jeep and start the re-install. a person could do a couple of these a day and not have to rush themselves much at all,seriously.

dirty d said:

apply sealer to pan,get back under jeep and start the re-install.

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Careful on this one. Felpro's oil pan gasket for the 4.0 is a Permadry gasket...meaning you don't put any RTV or sealer on the pan or gasket. Simply (relatively speaking) put the gasket on the pan and shove it back under the Jeep.

Couple of notes to clarify on what the OP mentioned.

-Zip Ties...GREAT idea..wish I had thought of that before spending an hour trying to get the pan pack on without disturbing the gasket. Next time I do one on a 4.0 i'll remember to do this.
-Bearing Brace...I believe that's a 97+ thing..the earlier models don't have that brace.
-Bellhousing Bolt...if it's the one i'm thinking of, you don't have to take that or the nut out. All you have to do is loosen it as there is a cut out on the inspection plate so that it just slides in between the bellhousing and the nut.

UNCC_99XJ said:

Careful on this one. Felpro's oil pan gasket for the 4.0 is a Permadry gasket...meaning you don't put any RTV or sealer on the pan or gasket. Simply (relatively speaking) put the gasket on the pan and shove it back under the Jeep.

.

Click to expand...

that`s right.the last one i did was a cork fel-pro which i did use sealer on. the permadrys aren`t supposed to need it but i still cheat with the and put it in the corners.

UNCC_99XJ said:

Careful on this one. Felpro's oil pan gasket for the 4.0 is a Permadry gasket...meaning you don't put any RTV or sealer on the pan or gasket. Simply (relatively speaking) put the gasket on the pan and shove it back under the Jeep.

Click to expand...

Don't know about the Permadry gasket but the factory later one piece silicone gasket does in fact require 4 dabs of RTV.

"Apply Mopar® Silicone Rubber Adhesive Sealant on cylinder block to rear main bearing cap corners and cylinder block to front cover joints (four places)"

All 00-up 4.0L's use a different rear main seal design that requires the use of two dabs of Mopar® Gasket Maker which is a red anerobic sealer between the block and main bearing cap per the service manual location.

For easier access to the oil pan unbolt the front shocks at one end, remove the wheels and put the body as high as you can on jackstands. The axle will drop further out more room to get the pan off.

Use a spray trim adhesive on the gasket/block to hold the pan gasket to the block while you reinstall the pan.

When getting a brass punch get a thick one and just grind the tip only to the necessary diameter. Use a 3-5lb sledge to loosen the old baked in place rear main seal. Use a socket extension and tape if needed to make the punch longer if stuff is in the way.

All the internal bolts on the 4.0L are US sizes (including oil pan, valve cover, rods, mains, timing, etc...).

dave92cherokee said:

Some helpful info but it should be noted that these issues don't apply to all xj's. I've changed the RMS in my 92 and 93 and didn't have any of the problems you say you had.

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That's exactly why I posted this. None of these items are covered in the RMS writeups, such as the one that 5-90 did.

I used gasket sealer on my felpro gasket. No leaks yet after several days. That's good because I thought my FMS was bad also. I did forget to mention to purchase brass punches that are turned from hex-bar. The punch will fit in a socket, connected to an extension. I actually tried my hydraulic jack on the extension/punch, but it just bent instead of moving the seal.

Markos said:

This is a short list of items that I didn't read about in any of the writeups. Most of them were non-issues, but worth mentioning

• Many of the oil pan bolts have studs protruding from them, make sure you have a deep socket. Many writeups suggest replacing with stainless. Good luck finding these special bolts in SS.
• The bearing brace on late model XJ's is held to the bearing cap bolts via studs that protrude from the bearing cap bolts. Make sure your bearing cap socket is a deep socket.
• Most writeups "can't remember" size of bearing cap bolts. 3/4" is too small. 13/16th fit the best, but felt a tad sloppy IMO. 20mm and 21mm sockets don't fit. I used 13/16ths.
• If you have a factory front skid, allocate time to remove this as well. You may be able to work around it, but it blocks access to many oil pan bolts, and you risk smacking your forehead on it.
• Brass punches bend really easily
• It's pointless trying to keep the oil pan gasket lined up with the oil pan while reinstalling. You can use zip ties to keep the gasket in place.
• '99+ XJ's have an oil pan support bracket that gets int he way of the two large oil pan bolts near the bell-housing. You should be able to jam your socket on these bolts, bending the rubber out of the way. The rubber may crack, requiring a new support bracket.
• One of the large bell housing bolts that holds on the inspection plate will hit the exhaust downpipe before the nut can be removed. Be prepared to bend the inspection plate with pliers to facilitate removal

Click to expand...

From what I can tell, most of those stupid studs you mention are not actually used - some have wiring harness clips, transmission cooler line clips, etc on them but most can simply be cut down.

I really like the zip tie idea. I'm going to have to steal that one.

As for the exhaust downpipe - on the 98 I was working on recently, the downpipe was connected to the header with two (very rusty) bolts through a flange. When I do my transmission (should be this weekend, been meaning to do it for several days now, haven't found time) I'm going to cut those bolts, drop the whole exhaust out of the way, and work unhindered, then replace the bolts with new - probably either brass or stainless hardware.

pierceME311 said:

I waited until my motor was out to do my rear main, I think it would have been a living nightmare to do it in the jeep. The problem is made worse when you've hot a stud girdle that has to be removed and then re-torqued. Getting a long torque wrench towards the front, PITA!!

And it's really not that hard to get the motor out if you have a hoist, if you compare it with doing the rear main in the jeep it's way easier than an in jeep rear main replacement.

Click to expand...

Getting it out is easy... I don't really feel like putting it back in though :looney:

Also, due to the typo on "got" vs "hot", I misread that as "hot stud girlie" and was extremely confused for a second.

Markos said:

That's exactly why I posted this. None of these items are covered in the RMS writeups, such as the one that 5-90 did.

I used gasket sealer on my felpro gasket. No leaks yet after several days. That's good because I thought my FMS was bad also. I did forget to mention to purchase brass punches that are turned from hex-bar. The punch will fit in a socket, connected to an extension. I actually tried my hydraulic jack on the extension/punch, but it just bent instead of moving the seal.

Click to expand...

I'd compare this to a cheater bar vs an impact wrench... both have their places, but sometimes you just need more peak torque/impact force to "break the bond" than you can get with a source of constant force like a cheater bar or hydro jack, then after that it'll move easily.

UNCC_99XJ said:

-Bellhousing Bolt...if it's the one i'm thinking of, you don't have to take that or the nut out. All you have to do is loosen it as there is a cut out on the inspection plate so that it just slides in between the bellhousing and the nut.

Click to expand...

Yeah the bell housing bolt doesn't need to be removed. I wasn't able to easily remove the inspection plate without bending it (no big deal, bends easily). Also, it may be easier to remove the inspection plate if you remove the oil pan support braket first. Of course,

Originally posted by kastein
From what I can tell, most of those stupid studs you mention are not actually used - some have wiring harness clips, transmission cooler line clips, etc on them but most can simply be cut down.

Yep. There are about 8 or so oil pan bolts with studs. Of that, two were used for metal transmission line mounts. One is used for a metal O2 sensor plug mount. one is used for a plastic O2 sensor wire tie. The other four or so are in random spots and appear to serve no purpose.

Click to expand...

Click to expand...

Markos said:

This is a short list of items that I didn't read about in any of the writeups. Most of them were non-issues, but worth mentioning

• If you have a factory front skid, allocate time to remove this as well. You may be able to work around it, but it blocks access to many oil pan bolts, and you risk smacking your forehead on it.
• Brass punches bend really easily
• It's pointless trying to keep the oil pan gasket lined up with the oil pan while reinstalling. You can use zip ties to keep the gasket in place.
• '99+ XJ's have an oil pan support bracket that gets int he way of the two large oil pan bolts near the bell-housing. You should be able to jam your socket on these bolts, bending the rubber out of the way. The rubber may crack, requiring a new support bracket.
• One of the large bell housing bolts that holds on the inspection plate will hit the exhaust downpipe before the nut can be removed. Be prepared to bend the inspection plate with pliers to facilitate removal

Click to expand...

x2 on the engine skid.

I could not find a brass punch so I used a small diameter nail punch and a lot of care to avoid scratching the upper bearing cap.

I considered your zip tie idea, but went with rubber bands. Easier to remove, IMO.

Ditto on the rubber pan bracket. Getting the socket on that sucked at first, then I figured out that it was not that difficult. I swore some at first.

I was able to get my inspection cover off without removing the bolt by the downpipe and without bending that part of the inspection plate. Yes, I'm that good.

Well, my RMS still leaks and I will need to redo this job. I'm that bad.

After thinking of what went wrong, I believe it is because I used anerobic RTV on the front and rear curved portions of the pan gasket and not just the corners, as per one of the online guides I used. I hope the RMS is good and the leak is coming from the pan only.

As an update to my last post, my RMS stopped leaking over the last few days. I was going to get back on it, but there is not urgency. Maybe it took a while to get a good seal. So odd.

I love it when problems solve themselves like that. Happened with the thermostat gasket on my MJ, too, I put it all together and started it up to test it and it was spraying coolant from a pinhole... said forget it, I don't care, threw two gallons of premix behind the seat and a day later it wasn't leaking anymore :dunno:

rocknxj said:

x2 on the engine skid.

I could not find a brass punch so I used a small diameter nail punch and a lot of care to avoid scratching the upper bearing cap.

I considered your zip tie idea, but went with rubber bands. Easier to remove, IMO.

Ditto on the rubber pan bracket. Getting the socket on that sucked at first, then I figured out that it was not that difficult. I swore some at first.

I was able to get my inspection cover off without removing the bolt by the downpipe and without bending that part of the inspection plate. Yes, I'm that good.

Well, my RMS still leaks and I will need to redo this job. I'm that bad.

After thinking of what went wrong, I believe it is because I used anerobic RTV on the front and rear curved portions of the pan gasket and not just the corners, as per one of the online guides I used. I hope the RMS is good and the leak is coming from the pan only.

Click to expand...

FYI - I still haven't re-installed the rubber oil pan brace. I have a new one that I got from the dealer, but I haven't had the time to crawl under the jeep and install it. I also need to re-install the front skid, but I figured I'd procrastinate until I take the Jeep wheelin'.

I changed mine on the 2000 a few weeks ago.

Where did you find the RMS for the 2000 and what is the PN? I got the older style RMS and cut the ears off. It's leaking waaaaay worse than before. The seal was oriented the same as the one it replaced.

I want to say it's fel-pro 40184 but don't quote me on it.

Will check my references and update...

EDIT: swing and a miss, it's Fel-Pro BS40612.
EDIT2: that's really strange, that's the one that is also listed for a 98 and other earlier years. Checking further...
EDIT3: Apparently the new design was introduced in 2001, at least according to RockAuto. I was one off, the new design is Fel-Pro BS40183.
EDIT4: Checking my MOPAR catalog set however, the new design was introduced in 2000. Gasket set 4740008AC for 99 down, gasket set 5017432AA for 00 up. This set includes much more than you need though.

Why are you guys pulling the inspection plate? I'm going to assume that this is an auto thing? I just did mine three weeks ago and never pulled an inspection plate of any kind. That said, I'm a 5spd.

Glacialbass said:

Why are you guys pulling the inspection plate? I'm going to assume that this is an auto thing? I just did mine three weeks ago and never pulled an inspection plate of any kind. That said, I'm a 5spd.

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I pulled the inspection plate the first time a few weeks ago, didn't pull it this morning and everything went fine, except I can't find that gasket anywhere locally.