Overheating issues

[Merkatroyd]

Hello all, first post,


My XJ 4.0L won't stop overheating. (in park or driving)



This is a long and complicated story, I will try to keep it simple: Me and a friend replaced the motor in my jeep with a motor from another jeep 2 weeks ago. The jeep began overheating, and I noticed the water pump was leaking, so I replaced it, but the overheating continued. (It also got coolant in the oil when it overheats, a problem which disappeared after I replaced the head gasket.)

I removed the thermostat, placed it in boiling water, it opens and shuts just fine at the right temperature (195 degrees) so that isn't the problem. However, I replaced it anyway with another one which I also tested. I replaced the temperature sensor located at the front of the cylinder head next to the thermostat. The fan shroud, radiator, and electric fan have all been replaced about 1 year ago in an unrelated project. I also replaced the fan clutch too. the problem still persists. I made sure there were no air bubbles in the motor either. I parked it on a hillside facing upwards, and filled the coolant until it was flowing out of the cylinder head.



The only time it won't overheat is if I remove the thermostat completely. Then it just runs a little cold, maybe 115-130 degrees.



Anyone have any ideas why my car won't stop overheating?

 

[RCP Phx]

What year?

 

[Merkatroyd]

What year?

I should have included that. It is a 1993 Jeep Cherokee XJ with a 1994 engine swapped into it.

 

[Unclewolverine]

Good chance changing the engines stirred up crud and clogged the radiator. It dosent take much.

 

[RCP Phx]

The wrong water pump, a clogged radiator, or your running lean!

 

[Lost_Wrench]

Are you still observing actual physical signs of overheating or are you just going off of the temp gauge on the instrument cluster? I've had a broken temp sensor gauge (the one near the back of the valve cover gasket that communicates with the instruments) show false temp readings before like it was overheating. I removed it and found that it felt loose and broken so I replaced it and got accurate temp readings again. I probably hit it or bent it while working on something else near it.

Have you done a radiator flush to see if fluids are flowing through it smoothly?

 

[Merkatroyd]

Are you still observing actual physical signs of overheating or are you just going off of the temp gauge on the instrument cluster? I've had a broken temp sensor gauge (the one near the back of the valve cover gasket that communicates with the instruments) show false temp readings before like it was overheating. I removed it and found that it felt loose and broken so I replaced it and got accurate temp readings again. I probably hit it or bent it while working on something else near it.

Have you done a radiator flush to see if fluids are flowing through it smoothly?

I have also replaced the sensor located on the back of the cylinder head too, because I accidentally snapped it while doing something unrelated. Maybe the new sensor is bad? I haven't observed physical overheating signs, because I usually shut the car off when the gauge starts climbing beyond the normal temp range.



Before I do anything else, I will follow the advice of everyone in this thread and flush the radiator. I will post an update as far as if this fixes the problem.

 

[Merkatroyd]

Flushed the radiator. problem is gone. Thanks everyone!!!!