Overheating...sometimes...help

[BOLO1994]

Hi all. Wonder if anyone has had this problem. I have a 1999 xj, 4.0l. Recently had to change the hoses on the radiator due to leaks. Since the change I have experienced radical overheating problems that come at intermittent times. I have changed the thermostat twice, the temp sensor, the water pump, flushed the radiator twice and burped the system. I do not think there is any air left in the system. Anyone have any helpfull hints out there? Oh, I did forget to mention, the operating conditions are usually with the AC on upon onset of overheating. The temp drops back to normal like a brick if I turn the AC off and occasionally have to tunr the heater on. As soon as I get back to a normal temp, I can run the AC with no problems. Thanks for any help ou there.

[Sig220]

Have you checked the "auxilary" fan to make sure it works? That would be the electic one.

At least I "think" the 99 has the electric fan like the 96 and others do.

[RichP]

Turn the A/C on with the hood open and parked, the electric fan should go on and off in synchronization with the A/C compressor. Also does the bottom hose you replaced have a spring inside ? The factory ones do, if it does not the hose can be sucked flat by the cooling system which will cut off coolant flow to the water pump.. Might want to replace the pressure cap too, they do go bad, I replace mine every other year with a new one..

[BOLO1994]

Hi Rich,
Yes the AUX fan is working, and when I replace the bottom hose I re-installed the spring. I will try the pressure cap tomorrow. I did however find that my tranny fluid was about a quart low. That being the case, could the remaining fluid in tranny have gotten super heated and when it passed through the radiator/tranny cooler system cause the engine overheating? Thanks for the help. Steve