There is an engine oil leak in my Cherokee. I went to the garage to fix it. They said it is from a gasket inside the engine, and the gearbox must be removed to fix it... What gasket is it

 

That would be the rear main seal which isn't actually inside the engine. It sits on the back of the engine, between the crank shaft and the oil pain. Hope that helps.

 

thanks!!! A photo please!!

 

Its the seal between the oil pan and the block. If you aren't familiar with engines, its the seal that goes around that round thing (crank) in the middle there.

 

thanks, but is it a big job to replace it? and is it a common problem in Cherokees?

 

Yes, and Yes. You have to drop the transmission to do the job.

 

do you have a 4.0 I6 ?? if you do you dont have to pull the tranny you can do it all just by dropping the oil pan i just did mine only took a couple hrs heres a couple write ups
http://go.jeep-xj.info/HowtoRearMain.htm
http://jeepin.com/features/rearmain
only thing im not sure of is theres some years i guess with a 1 piece seal in that case you would have to pull the tranny just do a little google search

 

Moderately, yes, and no you don't have to drop the transmission.

The rear main seal used on AMC engines is a "two-piece" design, and you have to remove the oil sump and rear main bearing cap. The top half of the seal can be pushed out using a brass rod (use brass so you don't scuff the crankshaft - bronze or aluminum will work as well) and the lower half can simply be peeled out of the cap.

Use the 1996-up oil sump gasket (if you have the choice,) since it's one-piece moulded rubber and will give you a seal more easily than the older four-piece gasket. The rear main seal proper is pretty much the same all the way up.

Drop the seal halves in a cupful of clean engine oil before you install them - let them soak for at least an hour (I'll usually pour a cupful of oil and drop the seal in before I start pulling the oil sump.) This makes the seal more pliable, and lets it seal much more quickly (and makes it considerably less likely that you'll scuff the seal lip. And makes it easier to install...)

The lip of the seal forms a sort of "V" shape with the seal body - the open side of the seal should face the inside of the engine (get it backwards, and you'll be doing the job again - it won't seal.)

Get a torque wrench if you don't have one - torque the main bearing cap screws to 80 pound-feet, the small oil sump screws to 7 pound-feet/84 pound-inches, and the large oil sump screws to 11 pound-feet/132 pound-inches.

It helps to remove the starter motor before you remove the sump. Don't mix up the screws - they're usually one inch and one metric (don't ask me why.)

This can be done in an after-noon in the driveway, if you're motivated. If you're not heavily experienced, expect it to take six to eight hours instead (my personal best is about 3:45, beginning to end.)

The other posters may be thinking of later-model engines. For most automakers, the "one-piece rear main seal" idea has caught on a good twenty years ago, and you do have to remove the transmission for those. AMC engines, as I recall, have never had a one-piece rear main seal - they've always been two-piece jobs (the two-piece rear main also tends to be somewhat less expensive...)

 

you're awesome.

 

Actually there are double lip seals on sale on e-bay for cheap that i would buy instead of the single lip original seal. The toughest part is to separate the oil pan from the block, it took me a couple of hours and a ton of bad words to cut the gasket all around...

 

Use a flexible putty knife to get in there. It's thin enough to drive past the OEM seal (which is mostly silicone, I think,) flexible enough to go around curves and to not pull the sump lip down to where you have to straighten it, and strong enough to be used to prise the sump off. It's what I use.

Don't need to use sealant on the moulded rubber gasket, either. I never have - and I've done this job at least a half-dozen times now (sometimes on a vehicle that belongs to someone else, too! I've had five XJs so far, and I've done rear mains on three of them...)

Fel-Pro makes a double-lip seal as well, and I'm sure Victor-Reinz (Dana) does also. I wouldn't buy a "knock-off" brand for something like this - Fel-Pro is as cheap as I'd go. It's a difficult enough job that you don't want to do it again for at least ten years...

 

My bad.. Didn't know it was a two piece.

 

I replaced the rear main seal on mine while laying on my back with the front end about a foot off the ground. I love the 2 piece design of these things! LOL. The top part of the seal can be pushed out with a soft metal rod (brass, aluminum, etc.). Much easier to replace than the rear seals on the Dodge 2.2/2.5's (much experience on those!)

 

many many thanks to all

 

I used the original seal and i still have a drop every two or three days of driving.. The journal was pretty much grooved, i wish i had used the double lip.
My oil pan was never removed since the engine was assembled in 1988 and the cork gasket was really really tough to cut through. At one point i was so desperate i put a jack between the front tire and the pan but it just bent a notch in the pan. Then i started kicking it and i ended up with a swollen foot.
At that point i didn't care much wether i would destroy something or not and i decided to hammer a huge screwdriver through the front corner.... nothing.
The corner was bent down but the pan was still there.
It finally fell off when i managed to cut the gasket all aroud with a razor blade and my fingers looked like i had sticked them in a pencil sharpener.
Let me find some pics...