Symptoms
Oil on the driver's side of the block and dripping off the crossmember. Comanche Club members warn that a bad adapter O-ring is often misdiagnosed as a rear main seal.
The fix, step by step
- Clean the engine so you can see where the leak starts.
- Drain the oil, remove the filter, unbolt the adapter, clean both faces, fit new O-rings and refit.
- Use the 1987–92 O-rings for the MJ's 4.0.
- Note that Renix-era engines use a metric filter thread; a Comanche Club write-up covers converting to an SAE filter.
Tools & part numbers
- Sockets
- filter wrench
- drain pan
- degreaser
- rags
Where to buy the parts
Crown 33002970K oil filter adapter O-ring kit, 1987–92 XJ & MJ 4.0LQuadratec ↗Amazon ↗
Crown 33002970 oil filter adapter O-ring, 1987–92 XJ & MJ 4.0LQuadratec ↗Amazon ↗
Hunting a used or discontinued part? Search eBay Motors for Jeep Comanche MJ parts →
Rated for a competent home mechanic with a decent tool kit. Confirm torque figures, fluids and procedures against the factory service manual for your VIN, support the truck on stands rather than a jack, and work at your own risk (disclaimer). Some parts links are affiliate links, which pay us a small commission at no cost to you.