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HadeReed 05-16-2011 03:10 AM

Over Heating...HELP !!
I have a 1990 XJ Sport 4.0 motor.
I have replaced the water pump (and not with a cheap "everlast") and "burped" the cooling system 3 times today (I also changed the thermostat) in a matter of hours and each time the pump is squeeling in 5 minutes or less. Yes I am positive it is the water pump squeeling....POSITIVE. Took out radiator and water from garden hose flowed through it just fine, but still taking it to shop to be checked.

Whats perplexing me is two things 1). Upon the third pump squeeling, something told me to check the thermostat . I did dis-assemble thermostat housing while motor was still hot. As expected the thermostat was open. What was NOT expected was there was hardly any antifreeze AT ALL when I rmoved housing to thermostat...???????

2). Someone told me there was a "By-pass Valve" on the block for the cooling system and that it could be blocking water flow. Does anyone know about a "bypass valve"?????????????????

4.whoa 05-16-2011 06:41 PM

Re: Over Heating...HELP !!
There's no bypass on the block. there is a bypass valve for/in the heater hoses. When I fill mine I use the temp sensor as an air bleed. It helps a little

1992XJ_Cherokee 05-19-2011 03:20 PM

Re: Over Heating...HELP !!
how is your rad fan clutch?

Frango100 05-20-2011 09:21 AM

Re: Over Heating...HELP !!
I know that there are 2 types of waterpumps available for the 4.0 who have a different rotation direction. If you have the wrong one, for sure the engine will overheat.

rockchucker 08-15-2011 05:57 AM

Re: Over Heating...HELP !!
The easy way to purge the air out of that system is to park on a slope with the front pointing down and the rear up in the air, then you can remove the temp sensor located at the rear of the motor right by the fire wall on top by the valve cover. Allow the motor to warm up and purge the air out and put the sensor back in, this will get rid of the air pocket in the motor. I know this is late but hope to help.

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