I was in a drive thru for longer than a half and hour( pretty dumb of me)and noticed my truck was about to overheat. when i turned it off and back on it started at a high rev. I just put in new coolant and a radiator a week prior and as soon as I start driving it cools down. the radiator fan works fine and i didn’t have the ac on so i assume because its a old truck idling for a while will get it hot and its 93 outside but wanted some extra feed back. I popped the hood open and the reserve tank was full and their was no oil or anything anywhere so my engine seems fine pretty hot but fine.
Either an air bubble… which isn’t indicated by the full reservoir… or that fan isn’t working like you think it is. If it has a fluid filled fan clutch, that is a likely source of the problem. RockAuto only sells the fan clutch attached to the water pump.
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Sounds to me like an inefficient cooling fan, inefficient water pump, or possibly a defective thermostat or air bubble trapped behind the thermostat. If the fan clutch is part of the water pump, replace the assembly and be done with it.
I’d also replace the thermostat, and drill a small (1/8" to 1/16") orifice in the part which closes in order to assist with air removal. This is a common and accepted solution for many vehicles, and there are also thermostats available with the orifice pre-drilled, or with a jiggle valve installed.
No, it is not.,
I’m thinking bad fan clutch.
After vehicle sits overnight open the hood and spin the fan, it should be Cold Locked so won’t spin, you can move it but not spin it
If it spins easily replace fan clutch
Start engine, should hear fan sucking air if it was Cold Locked, then that noise will go away after 5 to 10 seconds, shut off engine
Fan should now spin easily, its fully unlocked
After you get home from a drive and engine/radiator is fully warmed up, shut off engine and spin fan again, should not spin, should be Heat Locked now
If not replace fan clutch
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To maintain proper coolant temp when idling, the engine compartment fan has to be working correctly, spinning as fast as it should. It may be your fan is spinning, but not as fast as it should. There are gadgets available which measure how fast the fan is spinning, but I doubt most shops have those. And it might be difficult to determine the fan speed specification for you truck in any event.
I have an older Ford truck myself. My truck’s engine compartment fan is directly connected to engine crankshaft via the fan belt, so as long as the engine idle rpm is correct, I know the fan is spinning the correct rate as long as the belt is properly adjusted & in good condition. If I had that problem, first step, I’d remove the thermostat for a look-see. If thermostat looked ok, and fan turned on & off at correct temps & rpm measured ok, next I’d remove the radiator, turn it upside down and flush it out. If a lot of grit came out, I’d pay a radiator expert to assess the situation. They might recommend the radiator be replaced and the engine receive a water pump flow test & a major cooling-system-flushing treatment.
Note: A faulty radiator cap can cause this. You might want to just replace it and see if it helps, probably won’t work, but it is a low expense, and at least you end up with a new cap.
Back up plan when this occurs: Keep AC off. Turn on heater to max heat and heater fan to max. That will provide a little add’l engine cooling. Open windows, will be very hot … lol …