my '93 4.0 with 130,000+ miles seems to be developing a overheating problem, but its intermitant. yesterday i pulled my 1,000 pound box trailer 25 miles, engine temp was a little higher than normal but not enough to worry much about. later i drove to work, was fine on the way there. when i got to work i waited for the shift ahead of me to leave from a meeting, i sat for about 20 min with the a/c on high, actually fell asleep. woke up and the temp guage was higher than when i pulled the trailer, not pegged out to the far right but over halfway of the needle sweep. i rolled down the windows, turned the climate controls to heat and ran the blower on high for 5 min until the temp guage dropped to normal. on the way home, it was fine, coolant level is normal, was last changed 3 years ago when i put in a thermostat. when iwas pulling the trailer i was only going 55 in 4rth, wasnt really working it hard, and it wasnt hot outside. im wondering if the fan clutch could be not working or if its something with the water pump. both are oringinal. if i get a new water pump is the "severe duty" worth it or just a extra 20 bucks? usually if i have something with a cooling system issue, its either working or running hot, not a intermittant issue.

 

engines are never able to cool themselfs while stopped at an idle (especially while running the AC) as well as they can while moving down the road because of the lack of cool air moving over the radiator. it is possible that the fan clutch is going but judging by the age of the truck and the mileage on the cooling system and its components the engine will probably tend to want to run a little warmer anyways. i wouldnt be too concerned with it, my 93 4.0 would do that too even after i put a larger explorer radiator and brand new water pump in it.