thermostat problems ?

jmac

New member
90 model cherokee 4.0 no thermostat when purchase install new one ran hot but both fans work any ideas ?
 

Check for water in your oil. If none, flush cooling system out, change coolant. make sure front of radiator is not clogged/ dirty.
 
Don't forget to check the water pump as well. IF you decide to replace the pump, make sure it's the correct impeler rotation.
 
Anytime you open the closed system 87-90 you are liable ot get some air in inside. Various methods for getting the air up to the canister, none of which work very well.
I've had reasonable luck crushing the top radiator hose repeatedly while the motor is running.
If it overheats at idle it is often the fan clutch.
If the top radiator hose gets rock hard and even swells when you rev the motor up it may be a partially plugged radiator.
Make sure the thermostat is installed correctly, most are stamped this side towards motor (or something similar).
Make sure you get a Jeep specific thermostat, it has a lower profile than say a standard Chev. The generic thermostat may fit in there, it may crush when you tighten down the elbow.
The first things to check is air, then cracks in the surge canister and the cap for the canister. The cap is actually a vent valve (opens around 15-16 PSI), if it sticks the air won't move to the canister. You can soak the cap is vinegar.
Other possibilities but these are the more common.
Like mentioned check your radiator for air flow, mine has looked fairly clean on the outside before, though it was partially blocked by mud where you couldn't really see it between the layers. Pollen, road trash, the fuzz from Cottonwood trees, bugs or whatever builds up.
The seal goes or the bearings then the seal goes and my water pumps leak occasionally, usually way before the impellers corrode enough to affect the flow any.
 
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