Rear Main Seal

-1990 xj with 4.0 liter/ 5 speed, and the rear main seal is leaking bad. Is the rear main seal a 1 piece or 2 piece? Repair suggestions welcome!! -Mike

2 piece and its no fun to fix...takes a long time, dirty. After a weekend i finally got mine in and i think it got jacked up during the process and its leaking again. if it gets screwed up, you should just get another one.

dont wanna hijack...but anyone have any pointers on getting the upper half in with out completely f-ing it up? i could not for the life of me get mine up in there without screweing the damn thing up....

Cant say for the 4.0 rear main...leaking, but havent fixed it, but i didnt have much trouble witht he 2-piece in my old chev. 350. i just lubed it up good, but some silicoln on the backside of is for lubrication, and rolled it up into place. when it got about halfway around, just took a blunt object, and pushed it around into place. one of these days i'll find out how hard it is to do the 4.0!

It's a two-piece seal - here's a summary write-up (I've memorised this for just this occasion, it seems this comes up every fortnight or so...)

Jack up front of vehicle and allow front axle/beam to fully droop.
Crawl under XJ and drain oil.
Draw about a cupful of clean engine oil, and drop both halves of new rear main seal into the oil. Let it soak while you work.
Unbolt and remove oil sump. This will slip out under the transmission, and will take a little finagling to make happen, but it will work (I did this on an 89 with no lift, so I know it's doable.)
Remove rear main bearing cap.
Using a brass or Nylon rod, push end of upper half of rear main seal until you see about a half-inch on the other side. Pull it out with a longnose plier.
Get top half of rear main seal out of oil bath and work it into place, noting direction of seal lip. The "V" under the lip should be toward the front of the engine, so any pressure will help seal rather than allow oil to pass.
Remove the lower half of the rear main seal from the main bearing cap and replace.
Apply a VERY small bead of RTV Black or Red to the ends of the lower half of the rear main seal such that it will "squish" between the two halves of the seal.
Apply a generous amount of engine assembly lubricant to the lower rear main bearing shell.
Install the rear main bearing cap. Torque bolts to 80 foot-pounds.
Install oil sump pan with new gasket. Torque 1/4-20 bolts to NOT MORE THAN 80 INCH-pounds (no more than 7 foot-pounds) and the 5/16-18 bolts to NOT MORE THAN 11 foot-pounds. Failure to pay attention to this may cause you to crush your gasket beyond servicability and result in you changing hte gasket again...

Lower vehicle. Start and allow to run at idle for one minute, then do at least three smooth "run-ups" to 4000rpm and back while watching oil pressure. You shouldn't have any trouble, but call it "cheap insurance" and make sure you don't have any changes.

I think it's about a four-beer job if you jump in and "Git-R-Dun!"

5-90

that was awesome man.
my name is mike moon, and i have a leaking rear seal.
(eeew dude)

http://www.jeepin.com/features/rearmain/index.asp

good write up on it

Not a bad writeup, but soaking the seal halves in oil while you work really does work better than the oil/soap thing (having done both with various engines, I finally settled on the oil soak) The long soak in oil will both lubricate the seal and make the outer part a little more pliant, resuting in a faster seal and longer service after installation.

The advantage we enjoy over most other engines using two-piece rear main seals is that we have a semirigid seal (pliant seal lips over rigid core) as opposed to the "rope" seal found in other engines - and the "rope" seal typically requires being cut to length, as well as a specialised toolkit to remove and install (and pulling that steel cable over the crank journal always did make me nervous...) And, our seal is constructed with an actual "wiper lip" rather than relying on absorbency and "wicking" to keep oil in the engine. I find the semirigid seal much easier to replace with the engine in situ.

5-90

I have never tried this suggestion (when I did my 87 the seal slipped right in), but have heard that for a really difficult removal and reinstallation you can loosen all the main bearings a little to allow the crankshaft to drop a small amount and give the seal a little clearance. Take that suggestion with a grain of salt - as I said, I've never had to try it, but it sounds as if it might work.

sorry to bring this back up, but I'm having an extremely difficult time getting the upper half of the seal out. I have tried poking at it with a small screwdriver (sorry, my toolkit is not complete enough to have a brass punch, lol), but it won't budge. I then loosened the serpentine belt and all the main bearing caps, making sure they dropped down about 1/8". I can't get the crank to drop though, any suggestions on how to do this?

oh, btw, it only took about 4 hours to get the pan off

:helpme:

I found a punch that was about the right size, it´s actually smaller than it looks like, because the seal has an odd shape to it. Tried both ends, hitting that thing progressively harder till she moved. Actually had to hit it pretty hard, was holding my breath. Was carefull not to get the punch over the edge of the seal and hit the block.
You can probably find something about the right diameter, maybe even a piece of wood. You want whatever your using as a punch as big as possible, so the surface area is as large as possible (so you deform the gasket as little as possible), but not so big it hangs over the edges.
It would probably be possible to pry the crank down with a piece of wood, towards the rear, wouldn´t drop it down more than 0.015 or 0.030, unless absolutly necessary. I just loosened the rear cap a little myself, don´t know if it helped or not. It would be a bumber, for a main bearing to pop out or shift. If it isn´t too late, don´t get the main bearing caps mixed up (a middle serious screw up), or backwords. I always mark them on one side near the bolt hole (sometimes they are already marked), number them front to rear. Even if they are already marked, I mark them again myself.

When I did the seal on my 87, a little piece of 1/8 inch brazing rod made a punch of just the right size. The brass won't mar the crank if it hits it. Keep it as short as you can so it doesn't just bend over.

8Mud said:

It would be a bumber, for a main bearing to pop out or shift. If it isn´t too late, don´t get the main bearing caps mixed up (a middle serious screw up), or backwords. I always mark them on one side near the bolt hole (sometimes they are already marked), number them front to rear. Even if they are already marked, I mark them again myself.

Click to expand...

no worries of that, the most I have loosened any of them is 1/8", just to make sure I don't have bearing popping out or getting mixed up

kragen sells a kit that has a wire with a screw type shape at the end, and a t-handle. i am sure you could make this from hardware store stuff. there is also a piece that makes it easier to install the new one, which is also a tremendous pain in the ass. i saw these after i had done mine the hard way, and i think they would have helped. i used a torx driver to get mine out, and the shoulder of the tool marred the block. it hasn't made a difference, but i am glad i didn't get the crank. with the kit (or a homemade one) you just remove the seal like a cork. good luck

PapaPump said:

kragen sells a kit that has a wire with a screw type shape at the end, and a t-handle. i am sure you could make this from hardware store stuff. there is also a piece that makes it easier to install the new one, which is also a tremendous pain in the ass. i saw these after i had done mine the hard way, and i think they would have helped. i used a torx driver to get mine out, and the shoulder of the tool marred the block. it hasn't made a difference, but i am glad i didn't get the crank. with the kit (or a homemade one) you just remove the seal like a cork. good luck

Click to expand...

The tool you describe is for "rope" type seals, NOT for the solid rubber type seals.

The seals used in a 4.0 are, by the way, rubber with a STEEL CORE inside to hold their shape. There is NO WAY the tool for removing the rope-type seal will work with these newer more modern seals on the 4.0

Changed mine out ealier today. Just wanted to say thanks for all the help. This post really came in handy. Still waiting to see if i did it all right, no leaks so far. Thanks
James

Just to add to the earlier discussion - the old upper seal in mine (183,000 miles) seemed pretty solidly in place; knowing that I was pushing on a steel core helped convince me to use a punch carefully lining it up before smacking it although I think it only took one to two pops on either end to make it move. I was about ready to grab an old chopstick that I removed several inches of the end if needed, but it proved unnecessary.

Once the seal is loose, there will be 1/4" to 1/2" showing. Grab that with a pair of needle-nose pliers and begin to pull it out but remember that the seal has a steel core and is round... Don't pull it straight down, but rather along the curve of the crank.

When installing the upper half, take care not to cram the seal into the opening, as you may start cutting the edges off if misaligned.

96+ 4.0L blocks will have a "girdle" that needs to be removed before you can get to the #7 main bearing block. This girdle straddles all the mains and helps lend rigidity to the underside of the block and I believe also helps reduce NVH (noise, vibration, harmonics).