The other day my wife took a trip out of town and the jeep overheated. She stopped and let it cool down, then came straight home. I changed the thermostat twice and cap but that didnt fix the problem. I start the engine and the temperature gauge says its over heating in a matter of minutes. The water in the radiator goes up then down up then down. I fill then it comes back out. I check the inlet hose and it has alot of pressure on it but the thermostat seems to never open. I am wandering if this may be my water pump. also the heat was working but now is not. I figured the water pump wasnt pumping the antifreeze that far back. any suggestions or answers would help. 99 jeep grand cherokee
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Re: over heating quickly
First, start engine and attempt to re-fill with the heater on hot. Sometimes they can get airbound. There is little chance this is being caused by the water pump. Far better chance that the radiator is internally plugged. Jeep radiators are notoriously small for the application and have little room for "error" Partial flow will cause this problem... I've seen it as the major reason aside from a head gasket failure for overheating (assuming you put the stat in correctly) I use a swimming pool pumpfilled with household "lime away" rust & lime remover (which is usually what obstructs core tubes). to backflush these, but you may wish to have a shop do it in a more "normal" way.To do this correctly, the radiator must be removed or rust will remain in tank.
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check to see if you have a viscous fan hub and if so then replace it . Check when the overheating occurs If it is at stop lights but cools down when travelling. It is the hub. If it overheats when going slow and under load it will be the hub. If it overheats when travelling fast then check the radiator for core blockage and have a compression test done to check for head gasket / cracks Run fault codes and check for blocked exhaust system --cat converter)
I doubt that the belt is the problem as you will be have problems with the charging and probably the air con. The most likely problem would be the thermostat. Thermostats have two purposes, firstly they stop water circulating when the engine is cold so that it can reach operating temperature quickly (which also gives you warm air quicker in the morning). Secondly it regulates the speed that the water circulates. If the coolant is circulating too quick then it wont stay in the radiator long enough to be cooled therefore causing the engine to overheat, the air con turns on a thermostatic fan to increase airflow so the cooling will improve that's why the temperature "returns to normal". You will find on colder days the temperature will drop "lower than normal" with the a/c on. It's worthwhile changing the thermostat as you will find that your car will actually run a bit more efficient on fuel. Also check that the fluid in the cooling system is proper engine coolant, that will help considerably with the proper cooling of the engine not to mention reduce corrosion of parts in the system which can be very expensive to replace.
Ok, to review, it got hot climbing a mountain, and stayed cool going down the same mountain ? Make sure the mechanic did replace the thermostat, and have somebody check the fan clutch. An exhaust restriction could also cause it to run hot under a load. There is a small chance the water pump impeller is shot inside the water pump and not pushing the coolant thru the system.
Sounds like the electric cooling fans are not engaging. There is a sensor that is usually found on the side tank of the vehicle that senses coolant temperature. When this sensor goes bad it does not start the electric cooling fans and then the vehicle overheats from the extra heat produced from the AC system and increased engine load. It is not the thermostat or it would overheat quickly upon startup in about 10 minutes. Check the electric fans. Should be two of them.
The thermostat is in the housing bolted to the intake that the upper radiator hose goes to. Check the Intake manifold for leaks, these are prone to cracking the Intake. Check the front crossover behind the alternator and check the rear where the heater hose is hooked.
The heating up as you build revs, to me, indicates a partially oped thermostat. If it hasn't been replaced, I would do so. It's inexpensive and easy enough to do. Make sure you get a gasket with it.
The rattling thing is another matter. Do you think it is the water pump that is rattling? Does it ever drip from under your engine all the time?
Hope this helps... Good luck!