Replacing the XJ radiator is a two-hour job that ends chronic overheating for good — and the choice between a stock-style replacement and an all-metal upgrade matters less than most forum threads make it sound.
The factory XJ radiator is a plastic side-tank over an aluminum core. It has one reliable failure mode: the plastic tank splits at a seam, usually at the upper hose neck or along the driver-side tank, and dumps coolant. The other slow killer is internal scale that plugs the tubes and quietly drops cooling capacity until the temp gauge starts creeping on hot days or long climbs. If you're chasing an overheat and the fan clutch, water pump, and thermostat all check out, a tired radiator is usually the answer. On automatic XJs the radiator also carries the transmission cooler in its end tank, so a cracked tank can mix coolant into your trans fluid — pink milkshake on the dipstick means the radiator, not a gasket.
OEM vs. aluminum — the honest version. You probably don't need a 3-row aluminum radiator. A fresh quality replacement with a working fan clutch and a good auxiliary electric fan fixes the overwhelming majority of XJ overheating. The community sweet spot is a quality all-metal 2-row like the CSF 2682 — it drops in with no modification, won't crack a plastic tank, and cools better than the original without the airflow and flow tradeoffs a thick 3-row core can introduce. Reach for a 3-row Champion, Mishimoto, or Cold Case only if you run low-speed crawling in 100°F-plus heat with a built engine — Phoenix summers and a worked 4.0L being a fair case for it. For a stock or mild build, the Mopar/Crown OE replacement or a CSF 2-row is the right call, and it's the cheaper one.
Steps
Let the engine cool completely. Opening a hot, pressurized cooling system sprays scalding coolant. Don't rush this.
Drain the coolant. Open the petcock at the lower driver's side of the radiator into a catch pan. If the petcock is seized — common on older XJs — pull the lower radiator hose instead. Antifreeze is toxic to animals; contain it and recycle it. Removing the grille and headlight bezels (two to four Phillips screws each) gives much better access to the petcock and the radiator face, and takes five minutes.
Remove the fan shroud. Two to four M6 bolts (10mm head) hold it to the top of the radiator support. Lift the shroud up and rest it back over the fan blades — you don't have to fully remove it from the engine bay, free it from the radiator.
Disconnect the upper and lower radiator hoses. Loosen the clamps, twist each hose to break it loose, and pull it off. If a hose is hard and cracked, replace it now — you've already drained the system and a fresh set of hoses is cheap insurance against doing this job twice.
Disconnect the coolant overflow hose at the radiator filler neck.
Automatic only — disconnect the transmission cooler lines. The AW4 routes its fluid through the radiator's lower end tank via two metal lines. Use a flare-nut (line) wrench, not an open-end, so you don't round the fittings. Have a catch bottle and rags ready — fluid will run out. Cap or plug the lines to keep dirt out. Manual XJs (AX-15 / AX-5) have no cooler lines here — skip this step.
Remove the radiator mounting bolts. Two bolts (13mm) hold the upper radiator brackets to the core support. The bottom of the radiator sits in rubber isolator cushions in the support — no bolts there.
Lift the radiator straight up and out. Tilt it toward the engine to clear the support, then lift. Watch the lower fins and the trans cooler lines on the way up — bent fins cost airflow and a kinked cooler line is a new problem.
Transfer the rubber lower isolators to the new radiator if it didn't come with them. The radiator floats on these cushions; running it metal-to-metal on the support cracks tanks and fatigues the core.
Lower the new radiator into place. Seat the bottom pegs into the lower isolators first, then settle the top into the brackets. Reinstall the two upper bracket bolts — these are light-duty fasteners, roughly 9 ft-lb (about 105 in-lb). Snug, not gorilla-tight; you're clamping a bracket, not a head.
Automatic only — reconnect the transmission cooler lines. Start both fittings by hand to avoid cross-threading the soft aluminum tank, then tighten with the flare-nut wrench until snug. Do not overtighten — these thread into the tank and strip easily.
Reconnect the upper hose, lower hose, and overflow hose. Position each clamp past the bead on the radiator neck and tighten.
Reinstall the fan shroud and the grille/bezels if you removed them.
Fill the cooling system. Use a 50/50 mix of HOAT (orange, Jeep-spec) coolant and distilled water. The XJ system holds roughly 8–9 quarts. Fill slowly through the radiator neck with the cap off.
Bleed the air — the 4.0L traps it reliably. Set the heater to full hot, leave the cap off, start the engine, and let it idle. Squeeze the upper hose repeatedly to burp trapped air. The level will drop as the thermostat opens and coolant flows into the block; keep topping off. Run until the upper hose is hot, coolant circulates visibly, and no more large bubbles surface, then cap it.
Check for leaks and check your fluids. Run to operating temperature and inspect every hose connection, the tank seams, and — on automatics — the cooler line fittings. Recheck the coolant level cold the next morning and top off. On automatics, check the transmission fluid level and condition after a drive; you disturbed the cooler circuit and want to confirm it's full and clean.
Why it works
Ends chronic overheating when the radiator is the worn link — often the last piece after fan clutch, water pump, and thermostat check out
A quality all-metal radiator removes the plastic-tank failure mode permanently
Straightforward two-hour job with common hand tools; no special equipment beyond a line wrench for automatics
Trade-offs
On automatic XJs you're also opening the transmission cooler circuit — more mess, a line wrench required, and a trans-fluid check afterward
A 3-row aluminum upgrade is real money and overkill for most builds; the honest pick is usually an OE-style or 2-row metal radiator
Cooling-system air purging takes patience; a rushed bleed leaves you with mystery overheating after a clean job
Tools required
Socket set (10mm, 13mm)
Flare-nut (line) wrench for transmission cooler fittings — automatic only
Flathead screwdriver (hose clamps)
Drain pan (2-gallon minimum)
Phillips screwdriver (grille/headlight bezels, for clearance)
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.