Hi guys my buddy has a 01 WJ 4.0 and it randomly over heats he's changed the headgasket and the thermostat along with a radiator flush. The fan kicks on but we've noticed sometimes the fan will kick on a slow speed and others its very fast, when it kicks on slow it overheats is there something that controls the speed of the fan itself? Thanks in advanced!

 

Does it overheat while driving or at idle?

 

Yes, there is a PCM controlled pulse modulated relay that controls the fan and it's mounted underneath the passenger's headlight. It should kick on low at 195*F and high at 210*F. Once it kicks on, it will run slow until you shut off the engine. If it kicks on high, it will slow to low after the temp comes down to 195*F. You have to cut the plastic headlight bracket to get to it. Here's a picture;

 

Didn't 01 have the 0331 head?

 

Yes it did and I just went thru that. Supposedly it was fixed with the '02 models, but I installed an Odessa head from Clearwater, FL. $455 complete with valves.

 

Ok so we changed the relay under the headlight and it's still doing the same thing and it's only at idle when it overheats

 

at idle

 

We figured it out it was the fan itself it was seizing up, I hit with a hammer and it started working lol so we're replacing it now. Thanks for the help guys

 

Glad you found it. The fan was going to be my next suggestion. That relay tends to burn out if the fan amp draw as more than it should be. Just like your heater blower fan toasts the resistor.