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over heating


NAXJA Forum User
campbell, CA
Guys my xj is overheating only when I come to a stop and let it sit for awhile, but when im driving it runs under 210. any ideas? I have changed termostat, waterpump, and change to a 3 row radiator. and since that didn't work I decided to swap out the clutch fan and that didn't work either. what is it?

Well, I have seen this problem sometimes; many people correct it by installing a switch for the electro-fan, so when you come to stop, you can use the electro-fan as an additional help.

I think the cooling system of XJs are quite limited; in my opinion, you should have extra cooling capacity, which is not the case in this model if you ask me. So, you should also check that your coolant is fresh, that the radiator is clean (from the outside), that you have the plastic part wich resides on top of the fans, that your engine is in good shape (good spark plugs, clean filters, clean inyectors, etc).
Look into your aux fan turn on sensor. If your not over heating while driving, there is nothing wrong with your cooling system. To verify that it's the aux fan turn on sensor, turn on the A/C when driving, especilly when you're at a light. This will cause your aux fan to come on. Make sure the fan comes on ( to confirm the fan itself is not the problem ) and see if it still overheats.
well guys I tried to turn on the ac and the fan didn't go on so I changed out the relay and the fan still didn't go on. So what i did was unpluged the temp. sensor and the fan did go on. Now why wouldn't the fan go on when the ac is on? Does it matter if the ac is empty? please help by the way its a 92 thanks
Can't say for sure. I'd personally have to look at the wiring diagram to be able to see how the whole thing works, but I don't have one, sorry. Not familiar with the Cherokee off the top of my head either. It's an educated guess that a low A/C will not turn on the fan because the ECM looks for a pressure reading off the A/C sys also, but not 100% sure.

For starters, try driving around with the sensor unplugged to see if the Jeep still over heats.

Do you have a new temp sensor or a fan kick on sensor? Just want to clarify that we are talking about the same thing.
if your ac system isn't charged the fan wont come on because the compressor isn't coming on. But I have had so many problems with air pockets on my xj that I would say that is probably the prob. the xj cools about as well as i type. You are going in the right direction.The 3 core radiator is the best thing you can do for an xj. An electric fan is a good idea also. The thing I did to get air pockets out is go to autozone there's a bleed valve that you can install in one of the heater hoses. While you fill it back with coolant take the cap off the valve and raise the hose to thermostat level. When coolant comes out of the valve cap it off. you may have to do this a couple of times. Like I said this process can be a real pain in the a@* but good luck. If you've over heated it before it could be a warped head but nobody's overheated an xj like I have and I didn't warp a head. Good luck. DIRT
I have been fighting overheating also, replaced about everything. On the last try (water pump, 2nd one) i noticed my belt tension was not within spec (1/4 " play) in fact it was about 1" or so. Adjusted belt, is idling now for 3 hours at 190 degrees in the sun. Was it the pump or the belt tension? The old pump looked fine. Go figure. Hope this helps someone.

88 xj Pioneer.................death wobble fix next, i hope
Few things to look at...bear with me,as I have not worked on Jeeps in awhile...If your A/C is discharged the aux cooling fan will not come,the pcm will see A/C select input ,but will not turn on the compressor or aux cooling fan because it does not see the proper sense of charge from the low pressure switch.......second the pcm controls the aux cooling fan,it reads the coolent temp from the 2 wire sensor on your t-stat housing,also the pcm uses this sensor for reference on running parameters for the fuel injection...if the coolent sensor is not working proply,you would get a check engine light and/or driveblity problems...If I remember right,the PCM turns on the aux cooling fan at 221 or 227 degrees coolent temp( memory sucks)...........so alot of people have hard wired the aux cooling fan to a toggle switch to have command of the cooling fan on the trail to keep the temps down.....also a coolent mixture of 60% water to 40% coolent has helped,even try 70%/40%...but not in the winter :laugh3:...if you have access to scanner,you can actually see the correct coolent temp that the pcm sees,as your gauge in the dash uses a seperate standalone temp sensor at the rear of the head just for the gauge,and the gauge in the dash is about as accurate as ...well...you know.................Hope this helps.......

Naxja Member #114 :wave:
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OK, I tried loosening the fan belt to see if the temp would go up. nothin doing. It is still running cool, without the aux fan i might add. I have an adjustable thermostat that kicks it on at about 195. Who knows?, maybe the extra flush helped when i changed the water pump?? This is really weird. I had it flushed by a pro for 100$. Worked for about 4 hours then overheated. Still running cool at 190 or so.