Jeep 4.0 Oil filter adapter leak

Jeep 4.0 Oil filter adapter leak

Jeep Cherokees and other Jeeps that use the 4.0 are subject to a leak on the side of the block where the oil filter adapter attaches. There are three O rings inside that with age will leak.

Often this leak is misdiagnosed as a rear main leak or even a valve cover gasket leak. When the oil filter adapter leaks oil is blown back and collects on the rear of the engine.

The proper O rings are available in a kit from your local Jeep dealer or form a Crown Automotive distributor. Standard O rings do not seem to fit, so you need to get the proper rings from the kit.

There are two different types of oil filter adapters used throughout the run of 4.0 blocks. One has a 5/8 hex on the surface. The later version has a T60 torx in the end.

Removal of the older hex version is pretty straightforward. Just turn the hex with a wrench and remove the adapter.

Removal of the later Torx version is more difficult in that there is not enough room to put a normal torx bit in the opening and still be able to put a racket on it. One method to gain clearance is to remove one of the bolts that hold the engine mount to the body. Getting this bolt head out of he way will give just enough clearance to put a 3/8 ratchet or breaker bar on the torx bit. As the center unscrews, you will run out of room before the part is all the way out.

One way to deal with the lack of clearance is to use a torx bit that can be fit in a box end wrench. Or you can make a special tool for the job by welding the torx bit into a box end wrench.

When the O rings are hardened, it takes a lot of torque to break it loose initially and there is a lot of friction all the way out until it comes loose. If you make a wrench, be sure to make it strong.

Once the adapter is off the block, you will need to remove the old O rings. If it was leaking, then they will likely be hard like bakelite. The big one often sticks to the bock. Scrape it loose or free it from the O ring groove depending on where it ends up.

The two on the center bolt are best removed using a dental pick. Coat the new ones in oil to slip them in place. Make sure they are seated in their grooves and not twisted when in place.

Set the adapter back up on the block. Align the roll pin with the groove in the adapter to ensure the proper clocking of the adapter.

Carefully start the center bolt into the bock and tighten securely. It does not have to be as tight as it was when it came off. It was stuck by the old O rings then.

Check the oil level, as you will likely have lost what was in the filter. Start the engine and check for leaks.

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