On XJ Overheating

[longfellow]

Ok...there seem to be too many threads with "my xj is overheating" or "yet another overheating thread" or "it only overheats when..." and I am going to try to answer them all and maybe we can get this to become a sticky or maybe posted somewhere.

All Cherokees from the factory have a cooling system which is designed to remove heat from the engine and transfer it away. Coolant being pumped by a water pump flows through cooling jackets/passages in the head and block of the engine. It flows around exhaust and intake ports and around the cylinders. From there it goes to the radiator which had hundreds of small fins to increase surface area and that allows as much air as possible to take heat away from the coolant and the cycle repeats istelf over and over.

Chrysler opted for a mechanical clutch style cooling fan to draw air over the radiator to cool at idle and slow speeds. Some models depending on options also have an electric fan for optional A/C or towing package which turns on with a/c (on 2000 and 2001 xjs it turns on with a/c only when pressure in the lines goes past 300 psi) or when coolant temperature exceeds between 218-224 degrees F.

When working correctly and all parts are maintained, this setup works great.

Here are some reasons your Cherokee would overheat (240+f) at idle but not at 30+mph:
Fan clutch worn out
Old coolant
Aux. Electric fan not turning on
Blocked radiator or coolant passages
Low fluid level
Low engine oil level
Water pump impeller wearing causing low flow at slow speeds
Clogged radiator fins or air blockage to radiator
Damaged fan shroud
Retards who upgrade engines and leave stock cooling system


If your Cherokee overheats on the highway 240+F:

Clogged passages
Stuck closed thermostat
Towing a heavy load up a grade on a hot day w or w/o ac on (temp. Overheat)
Contaminated coolant
Bad waterpump
Clogged radiator fins
Blocked airflow
Brakes sticking/ebrake on

If you overheat on the highway and NOT at slower speeds / idle:

Partial blocked passages not flowing enough for highway engine demand but flows enough at idle.
Radiator blocked or fins clogged for same reason above
Brakes sticking
Overloading


Also, xj's have tight engine compartments and they will run 220ish in the summer with a/c on or off and that is NORMAL for xj's. Other vehicles have different coolant temps that they are designed to run well at so don't do too much comparing such as " my Taco runs 210 even though I beat it half way to hell) That's great...I only like taco from taco bell and the one she gives me...but anyway

Another thing to note...fan clutches run about 40bux new depending where you go. With personal issues there is no TRUE way to test a clutch because they fail soo many ways (trust me). Next time your engine is getting very hot, open the hood and feel the air the fan is pulling...rev ER up some and if its not hurricane force, then replace that clutch. With the new body style xj's they upgraded the E-fan to a higher flow rate...so that might be an option for upgrades.
Please add on if you have anything extra.