Sooner or later it's gonna happen to ya... You'll go outside and see a big ol' puddle of oil in the driveway under your XJ. With the Jeep 4.0L it's usually one of three things: the rear main seal, a leaky valve cover gasket or bad oil filter mount seals. Since you're looking at this page we're going to assume you've checked your valve cover gasket and your rear main isn't the problem. (Yeah.... right....) (Ok - we'll assume your rear main seal isn't leaking THIS bad.)

After ya check the rear main & valve cover gaskets and you find gobs of oil on the side of the engine around the oil filter... it's not time to panic. This is a no-brainer and won't set you back but a few dollars. For a few bucks and maybe an extra hour (or less) added to your oil change you can fix this easily. The problem is the oil-filter mount o-rings are well known for getting brittle with age & heat so if your Jeep has a few miles on it they will eventually give up the ghost and leaks develop around the oil filter mount.

Let's Get Started!

Note! There are a couple of different o-ring styles.

HO engines have an o-ring 'kit' available w/ all three o-rings packaged together so in this regard... you're in luck! Just go to the dealer and ask for the "kit" with the o-rings together and you'll be ready to go. Getting the o-rings isn't much easier than that! The hard part will come when you start cussing that TORX bolt holding the filter mount on.

Early / RENIX engines require that you buy all three o-rings seperately as they do NOT interchange with the HO o-rings. This is due to the different center bolt (TORX vs. hex head) that retains the filter mount. No big deal - they're a stock item for the dealer. These o-rings may be available at your local auto-parts store as well - they aren't anything special but you must have the correct sizes to prevent more leakage!

Here are the dealer part numbers and sizes for the RENIX o-rings:

33002970 o-ring .799x.103
33002971 o-ring 1.296x.13
33002972 o-ring oil filter AD

Individual 4.0L oil filter mount o-rings from Jeep dealership.

Early RENIX 4.0L oil filter mount bolt being removed with box end wrench.

This is a early 4.0L mount which you can remove with a box end wrench.

Be aware that newer models usually have a T-60 TORX head fitting that is more difficult to access. SOME of you may also find allen head bolts here.
A note on tools here: Newer XJ's with the Torx & allen-head style bolt are a bit of a pain to remove but not bad with the correct tools. Don't try to fudge on tools here... you NEED the correct size torx socket if your bolt has a torx head!

S & K Tools (and others) make a T60 sockets with the Torx bit held inside by an allen screw that you can loosen to remove the bit.
The cheapest ( and nearly useless ) versions will be one piece... (DON'T get the one piece socket-bits!).
The next step up will have the bit -pressed in-. If you get the ones that are pressed in, you'll have to pound them out with a flat punch & a hammer as they aren't really intended to be separated. You may end up ruining the socket but it's the bit you're really after here.
Best is the high-grade ones where you can loosen an allen screw and remove the bit anytime. Either way, once you have the bit out, you just use the hex part with it's torx end inside of a box-end wrench (10MM???) which gives you enough room to work where the socket-bit won't fit with a ratchet.

One piece T-60 Torx bit / socket from a cheap torx set.

This is the one piece torx socket-bits generally found in cheaper sets.
You will have a tough time using one of these as there is not enough room for this style bit AND your ratchet to remove the bolt!

S & K Tools Torx set with removable bits. You can loosen the allen screw to use the bit without the socket. Very handy for this job!

These two-piece socket-bits by S & K have an allen screw that retains the bit inside the socket.
You can remove the bit from the socket and use a box-end wrench on it which allows you enough room to remove the filter mount bolt.

9/16" allen head bit & socket for those with that variant of the oil filter mount bolt. Look for one with a removable bit.

SOME XJ's may have 9 / 16" allen socket head bolts. You'll need to find an allen bit socket for these but be sure to get one where the bit is removable.

You can also cut down a standard allen wrench to about 1 1/2" in length. (Short enough to leave in bolt head and still remove bolt and filter mount.)

You'll insert either the bit, or the cut off allen-wrench into a box end wrench and use it to remove the bolt.

Update: Posted by tsc on J.U. - "I have a 92 ZJ 4.0 that was a very large allen wrench.... Not all of them were Torx."

Yay. Yet another variation of the Three-Stooges mentality down at Daimler-Chrysler to warm our hearts while lying on our back in a mud-puddle on a 33* day trying to figure out why the tool that fixed one XJ won't fix another...

Be aware that engine swaps from ZJ's etc are common and you might end up with an allen bolt here... and that some XJ's appear to have had the allen bolt as well.

Disassembled Jeep 4.0L oil filter mount showing brittle & broken o-rings.

Disassembled mount showing old seals that were so brittle they had snapped in two upon removal.

Preparing to reassemble the Jeep 4.0L oil filter mount.

Cleaned up the mount & repainted it. New o-rings shown on left.

Smallest o-ring goes on the oil filter mount bolt inside the groove shown.

Smallest o-ring goes here.

Medium sized o-ring goes on outside of filter mount and is sandwiched beneath the oil filter mount bolt.

Middle sized o-ring goes here.

Insert bolt into oil filter mount being careful not to damage the o-rings. A small amount of oil helps here.

Bolt with smallest o-ring fits inside mount with medium o-ring like this. I used a small amount of oil just to slip them together.

Largest o-ring goes on bottom of oil filter mount and is sandwiched between the block & the mount. Use a dab of axle grease to hold it in place.

Largest o-ring goes here. Hold it in place with some axle grease inside the o-ring's seat. Make sure it stays seated while you replace the mount and doesn't get pinched. Do NOT overtighten the mount's bolt specs for your type bolt.

Again: Get the correct o-rings for your mount! If your filter mount uses the Torx style bolt you will need the 'kit'; if you use a box-wrench to remove the center bolt you'll have to get the o-rings seperately and they MUST be the correct size!

If you have pics of your own repairs or can suggest other methods - please contribute your ideas (and pictures) to this article!

Revised on: March 6th, 2007

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