My 1996 F150 blew its radiator about 5 months ago and ever since replacing it and the thermostat it randomly overheats out of nowhere. itll shoot antifreeze from under the cap and make a mess but after refilling it it runs fine for a while. Faulty thermostat? clogged line? Blown head gasket? Water pump? Il be honest and tell you i blew the radiator ina mud bog so i was working it pretty hard haha, but still cant quite figure the thing out, any idea?

 

To me it sounds like you have a coolant leak, and it begins to overheat as the level lowers. I don't think it's just because there's air in the system - if there was, it'd do it all the time.

 

See the thing is il refill it and then maybe 2 days or so later itll do it again, and il refill it again and nothiong will happen for 3 months, its just so random. Itll overheat and then drop to cool and will barely break the midpoint on the guage, and itll just flip flop from cold to hot before it eventually levels out. I never see any puddles of coolant under the truck, which makes me start to beleive i may have a blown head gasket, yet my oil has no water in it??

 

It might also be a water pump, sometimes they leak only when the engine's running. You may check it for free play, it will show the chances of a leak in that point. You'll need a compression test to find out if the head gasket is fine. According to described gauge behavior, it might also be a thermostat getting stuck, but my bet is still a leak. Maybe other guys will be more specific

 

May be, im gonna do a compression test on it soon but im really thinkin i blew the head gasket, its ran kind of sluggish the past few days and doesnt seem as powerful as it once was, il for sure check the water pump. Im going to flush the system and blow all the lines and replace the thermo once again just to be safe

 

Bad radiator cap. happened to me. Its worth a shot.