I live in Gilbert, Az. My 99 Cherokee has a new cooling system (within 1.5 yrs, new radiator, therm, water pump, and hoses). I tried to go up north to St. Johns to visit a friend and I overheated about 10 miles outside of Payson (a long stretch up the mountain). The only thing I know that is wrong with my cooling system is the shroud (it's chewed up, cut up, and held on by zip ties by the previous owner). My A/C does not work, so I don't run it. Does the electric fan not run if the a/c isn't running? Should I look into aftermarket electric fans? Will venting the hood make a big enough difference? Any info or help you can give me would be greatly appreciated!!

 

I think the efan only runs with the AC, but I could be wrong.

Fan shrouds are an important part of the cooling system, try replacing yours if your sure everything else is working correctly.

 

I believe the e-fan will kick on under a few conditions, one is if AC is on, another is if coolant temp is over a certain temp. The XJ 4.0L needs the extra fan under load, or else it will overheat.
You can easily check the e-fan...unplug the coolant temp sensor from the t-stat hsg, the e-fan should kick on i a few seconds. This will also throw a code. If its still not kicking on, try unplugging the fan and running 12v directly to it.

 

I'd suggest u look at the entire cooling system....how old are all components? Standard cooling (no factory a/c) consisted of the belt fan only and they didn't overheat unless cooling system maintenance was neglected or a component failed. The ECU turns the efan on at 218F coolant temp or when compressor engages.

 

i know it sounds silly, but i didnt see a thermostat on that list of replaced parts. that would be where I would start.

 

you should be able to feel the upper hose. if it's warm when the truck is overheating, it's likely ok; but given that the whole system is relatively new, and that part is not on the replaced list, it might be cheap insurance. There should be a good overheating troubleshooting tree in your haynes manual.

 

Sorry, I didn't spell it all the way out, but it is on the list.

 

Thanks for the responses everyone. I'll get out there tomorrow morning when it is cooler out and check everything mentioned here.

 

Does it overheat on the highway, only at idle? With any overheating condition, the devil is in the details.

As DJB mentioned, the e-fan should kick on about 218. Be sure that it is.

Even though your cooling system components are relatively new, don't get tunnel vision and think that they can't fail. They can. If your cooling system is clean and you are having trouble on the highway with temps, I'd suspect the water pump more than any other component.

Don't forget about your radiator cap. Replace it. It is a critical component and often overlooked.

Good luck!