I’ve got an 02 F150 supercrew with the 5.4. A couple weeks ago, while towing my boat, when I tried to jump on the highway the temp shot up. Had to get on the Service road and run the heater to get the temp back to normal. Got home checked the coolant, added a little. Then never did it again. Until today. Same thing, jumped on the highway while towing the boat, temp shot up. Got it to get back to normal the same way. On the way home, driving slow, temp was close moving again by the time I got home. Does this sound like it could be the thermostat sticking closed?

 

Could be the t-stat sticking, the radiator could be partially clogged, the fan clutch could be slipping, or the water pump could have a broken impeller. It's hard to take a guess based solely on "the temp shot up."

 

 

Given the low cost, I'd suggest putting in a new thermostat if for no other reason than to rule it out. I replace mine when I change the coolant to hopefully avoid a thermostat problem during the time I own the vehicle. Because it only happens when you're towing, I'm thinking it might just be some other more pricey problem, but putting in a new thermostat would at least rule that out.

 

If it ONLY does it when your pulling the boat, then it might be load related.. Put a BIG LOAD on the truck and it gets hot. That would lead me to believe the radiator is partly plugged inside or outside. Might be a good time to FLUSH the inside out and change fluid......... and was external fins / coils with a garden hose........... nothing blocking air flow thru front end ??

 

I'll echo steve(ill) thoughts, only to add, that maybe contributing is that the transmission cooler integrated into the radiator could also have restricted flow. Don't forget to flush it as well. (presuming you have a automatic transmission)

You also might have a external transmission cooler that could also be restricted. When was the last time you changed out your transmission fluid and filter?

 

Nothing you would ever hear over the sound of the engine. But for now like others have pointed out already, your issue seems to be related to moments of heavy engine load. This is indicative of the radiator not being able to dissipate the heat fast enough or a weak coolant flow. If the radiator is original then it's 16 years old.

 

A partially blocked radiator loses cooling ability under higher heat loads.
Acts like a radiator that is too small for cooling area.
If the coolant is dirty and a lot of stain in the jug, it may be the cause has just caught up.
That would indicate the antifreeze has not been changed often enough over the life of the truck.
Good luck.