97 F150 4.6L, 138,000 miles: When the engine is cold, in the morning or after sitting for more than about 6 hrs, after driving for about 10 minutes the temperature gauge will spike to the top and the coolant will spew out of the reservoir cap. I shut the engine down, restart and it drives perfectly until I stop and the engines has a chance to cool completely. Any insight or info would be greatly appreciated.

 

Thermostat stuck in closed position. I don't think the radiator or engine block is clogged. I assume you have the belt driven fan and not an electric fan. If you don't know the history of the truck then flush the engine and replace the hoses and thermostat. It's easy on that engine. The driver side hose is expensive because it connects to 3 places instead of 2.

 

I agree with the thermostat being stuck closed, or partially closed, no matter it still needs to be changed. While in their flush out the radiator and replace with fresh coolant and hoses. I just replaced both of my hoses, the top one ran somewhere around $20.00 and the bottom one runs around $38.00 cause of the extra little hose coming out of it that runs to the resovior, it is easy to change though.

 

truehop, did changing the hose and thermostat fix it?

 

sounds like an airlock, thermostat stuck closed, no coolant in engine,