grap

I have a 1992 F150, took the radiator cap off to check fluid flow as it seemed to slightly overheat yesterday, as soon as the truck reached operating temp, radiator fluid blew out like a volcano. Thermostat?

Thanks,
G

dewman

When the fluid came out "like a volcano," was the engine running? Or was the engine running and when it got to operating temperature, you turned it off and then the fluid came out like a volcano? If the 2nd question, then you should know that you should never turn off your vehicle's engine while the radiator cap is off. The backward pressure will cause the antifreeze to come shooting out of the radiator. There is no real pressure while the system is running, unless you are overheating, that is why you can remove the radiator cap without any fluid coming out. If it's the 1st question, then I am not sure if that is a fault of the thermostat, or not. It could be overheating for any number of reasons.

grap

Engine was running, might be mostly water (just bought truck) and I live at high altitude, wonder if it was just boiling..

Good old Bill

Perform test again, have full of water, run engine and watch closely. Monitor the gauge and also the top hose. Top hose should be hotter than bottom, if it stays cold but lower hose is heating up, there is an obstruction someplace. Start at T-stat. Get back to us as there are other things to look at.

ratchetjaw

Replacing the radiator cap with a new one of the same pressure could help it too. That is a really cheap fix that is overlooked most of the time.

grap

Thanks everyone, I replaced the thermostat and the radiator cap, problem solved.

ratchetjaw

Glad it worked out for you...