Symptoms
Unexplained coolant loss, brown or dirty coolant, milky residue under the oil cap, and often a recent overheat. Wikipedia says the crack sits between cylinders 3 and 4 and often shows as a tan line with the valve cover off.
The fix, step by step
- Confirm with a cooling-system pressure test and by looking through the oil filler (no 'TUPY' mark means an original 0331).
- Drain the coolant and remove the intake and exhaust manifolds, the coil rail, the valve cover and the rocker assemblies, keeping pushrods in order.
- Remove the head bolts and lift the head off.
- Change the oil and filter, then flush the oil again after the first short run to get coolant out.
- Fit a revised or aftermarket head; never another 0331, and confirm the casting with the seller before you buy (Wikipedia notes even 'TUPY' heads occasionally crack).
- Use a new gasket and head bolts, torque in sequence to the service-manual spec, then refill and bleed the cooling system.
- Fix the cooling problem that probably caused the crack.
Tools & part numbers
- Torque wrench
- head bolt sequence and spec from FSM confirm in manual
- gasket scraper
- pushrod organizer
- coolant pressure tester
Where to buy the parts
Crown Automotive 53010334 cylinder head, 1999–2006 TJ/XJ 4.0L (listing doesn't state the casting; confirm it isn't an 0331 before buying)Quadratec ↗Amazon ↗
ProMaxx CHR640NB bare cylinder head, 1991–2004 4.0LQuadratec ↗Amazon ↗
Head gasket set, 1999–2001 4.0L Cherokee XJ (SGA11362)ExtremeTerrain ↗Amazon ↗
Cylinder head bolt, 1987–2001 2.5L/4.0L Cherokee XJExtremeTerrain ↗Amazon ↗
Hunting a used or discontinued part? Search eBay Motors for Jeep Cherokee XJ 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.