Hey guys, im having a some trouble with my truck overheating. Its been fine for a while until recently it started acting up. What happens is the truck warms up to operating temp fine, then the heat blows cold. Soon after this the engine (coolant) temp will DROP down below operating temp. Next the temp will shoot up to the point where it blows out the overflow tank and i have to shut it off. After that it comes back down to perfect operating temp and it runs fine. It happens on random occasions, prolly once every week and a half.
What do you guys think? faulty thermostat?

 

Throw a new thermostat in, I doubt its the radiator cap but its only 5 bucks for a new one, both easy to do. If its not that then you make have a bigger problem, these are similiar symptoms to what I just had which ended up being a blown head gasket.... The seal is broke between the cylinder and cooling system in the block so the combustion pressure ends up pushing fluid and air through the cooling system thus over flowing the over flow...... But remember, these are just thoughts, I'm no certified mechanic or anything....

 

Yea im probably just going to throw in a new thermostat real quick and then go from there. Thanks for the help.