I recently bought a 91 F150 4x4 4.9L six and have noticed a small coolant leak by the thermostat housing. Yesterday i let it warm up at idle for about 20min. and when i went to look at the leak, the radiator hose was swollen up at the housing, like it was ready to burst. Looked at the temp gauge and it was normal. Does this sound like the thermostat is stuck closed?
Thanks

 

could be a lot of things.

start using some rustbuster on those bolts.

and don't break them when removing them.

w.pump, thermostat, bad head gasket all could be suspect.

 

Thanks, i just was kinda stumped cause it wasn't overheating.

 

i left out failed hose.

that is where i would start.

 

Thanks, now a failed hose makes sense to me.

 

I would guess, blown head gasket, check radiator for bubbles when engine is warmed up.

Bubbles like the water is boiling hot, those kind of bubbles.

 

the thermostat on my 91 went today when i discovered it was not warming up, at all, i checked the coolant to find white bubbles in it and a small glimpse of oil...LOVELY! ... difference is my thermostat is currently stuck open, on the plus not possible to overheat it, on the bad, its winter and i have very little heat LOL

i would start with the hose, simple easy and cheap ... plus that is the first thing that pops into my mind, i see lots of silicone heater hose do this on the big rigs...

if it warms up the same as it usually does and gets to about the same temp it it unlikely that the thermostat is at fault, if its stuck closed truck will overheat in minutes, if its stuck open truck will never reach operating temp...

blown head gasket also usually means you will get oil in your coolant...run the truck for a bit, if there are white bubbles or slime in the coolant you have oil in the coolant.


but since you say the hose bubbles up and the truck is heating up same as usual im gonna put my money on the failed rad hose...