jeep grand cherokee overheating

radiator, crap block air through radiator hoses water pump buying wrong thermostats incorrect coolant, amount or mixture fan fan thermostat engine running hot -- bad timing, fuel, or mixture drag on engine, AC or other accessory drag on entire car while driving; brakes, driveline

Lots of things, including the water pump, clogged lines or radiator, or a bad temperature sensor leading you to think it's not overheating when it is. What is it doing when it overheads and is the fluid level low when that happens? if you look down the radiator do you see lots of crusty white stuff?

--scott

Lets add cracked head or block, or blown head gaskets to the already helpful lists.

Hi. You could have an air bubble in the coolant. Some cars have a plug or screw to bleed air high up in the cooling system. Check your manual or call a dealer service department and ask if your engine has one. If it doesn't you could disconnect one of the heater hoses from the heater core (if it's higher than the radiator cap). Hold the disconnected hose at the same level as the radiator cap and fill the radiator until coolant comes out of the heater hose. If you don't have air in the system you could have a bad radiator. Good luck.