I'm sure this question has probably been asked a few thousand times but, I'm going crosseyed sifting through all the posts.
Dealing with an overheating issue on my 90 XJ. I've replaced the t-stat, overflow bottle and cap. Next on my list is to test the fan clutch for possible replacement.

I've read on several posts that the E-fan only comes on above 218 temp or when the A/C is turned on. I noticed when it overheated that the e-fan did come on but, only after the needle was touching the red and coolant was already spilling onto the ground. The fan will come on if I turn on the A/C. I've actually prevented an overheat situation a few times by turning on the A/C because the temp needle will begin to drop almost instantly.

Is this normal?

 

Probably not. Sounds like the thermo switch for the fan is bad as well as your clutch fan.

 

Can you point me in the right direction as to where the thermo switch is? Both my service manual and motoralldata are a little vague on it's location.

 

I believe the sensor is in passenger side tank on the radiator.

 

Hamster, that switch is on the drivers side rad tank just above the lower hose. I also noticed that my xj will run hotter in traffic without the air on so I guess that means I have a marginal mech. fan clutch.

 

the problem is that what the sensor in the rad gets, is not what temp the coolant is in the head.

it can be. definitely good that someone said the fan clutch.

drivers side of the rad, by the airbox.

that can be it, but think of this also, i just had a similar problem.

do you have an auto? the radiator cools the engine coolant (duh) and cools the transmission fluid (also heats it up faster on start up). if your transmission is running hot, it will cause your truck to overheat as well. check your tranny fluid, in my particular case, it was low, and causing the tranny to run hot. i had to drive everywhere with the e fan on. put new fluid in, and the problem has gone away.

btw, 1987 jeep waggy auto aw4 np231 d30hp and d44.

 

Jakbob, I can fully understand about the auto trans cooler causing temp issues but I don't have to worry about that crap 'cause I got a stick. But still, very good point. Hamster, auto or third pedal?

 

oh the trans cooler thing was directed to the OP. ive never hear of that here in OEM tech so i threw it out there.