4.0 overheating while sitting still

[racsan]

its not overheating to the point of damage (yet) but ive noticed that if my truck is sitting for a bit idling (like 10-15 min,usually with the a/c on) it will have the temp guage over halfway towards hot, normally it doesnt move but 1/4 of the way on the guage. once i get moving it goes back down. i have fresh antifreeze and a new thermostat. im guessing its either the water pump or fan clutch. how do you check the fan clutch? could i permantly "lock" it up? i have 109k on the truck and to the best of my knowledge the water pump and fan clutch are original. if ive got a problem starting id like to get it now before it gets worse, driving around town doesnt seem to get too warm unless im pulling the 6x10 trailer.

[MAKG]

You shouldn't need to permanently lock the fan clutch. Sometimes they fail that way (not in your case, though). It makes the truck LOUD.

I'd suggest warming up the engine (might as well drive it around -- it will be faster), then shutting it off and feeling the back of the radiator for cool spots. If you find any, you need a radiator. If not, replace the fan clutch.

It would be a good idea to install a mechanical temperature gauge.

And if you do replace the radiator, you can replace it with a 2row. If you don't already have one, you'll need a fan shroud that fits it or you won't be able to close the hood (always get fan shrouds from the junkyard).

[envious8420]

you can also try spinning the fan by hand when the truck is off and cold.
if theres resistance the fan clutch is probably ok. if it spins freely its no good