I know what your thinking and its not the head gaskets....Sunday I replaced my thermostat gasket (the original was leaking coolent), put RTV on both side, put the thermostat back, all back together, ran the engine for a few minutes to make sure that the seal was complete, no leak. Monday I am driving my car to work and after about 10 minutes of driving at 65mph i see my temp gauge go from "O" on "normal" to "A"(Ive never seen the car get that hot before), I freak out and pull off the freeway. Limp to a gas station and pop the hood. Check the bottom radiator hose and its ice cold,top one is almost to hot to touch. So i think the thermostat is bad, its not opening allowing coolent to drain back into the radiator to cool off. So i limp to work, not going over 30, and let it sit for a few hours hoping the night cold will cool the engine enough that I canget home, I was wrong. Leave work a few hours later and the car over heads in a matter of 5 minutes driving, so again I have to limp home. Next day (Tuesday) get a replacement thermo and gasket, slap them on there and same thing happens. But this time the top hose it really hot, and the bottom one is mediumly hot (its hot to the touch but i can still grab it without burning myself). Pull the radiator cap off while the car is running and see coolent, but its not moving (not getting sucked into the block, no bubbles eaither), so I take the new thermo off and test it (put it in boiling water to make sure it does in fact open, and it opens...so I know it works! I am lost on what the problem is[&:]...any help please

Thanks,
Matt

 

My mustang had this problem when I first got it. The thermostat was intalled backwards on mine. Lol. Guy I bought it from was not mechanically inclined I guess. Are you losing any coolant, like spewing out of the overflow tank?

Oh duh, my corvette had this same problem even after a new thermostat, take out the thermostat and drill two small holes in the top of it so alittle coolant can flow, you most likely have an air bubble stuck under the tstat, thus not allowing it to open.

Air bubbles usually form after doing service to the cooling system, like changing a thermostat gasket.

 

Sounds like an air pocket to me. If you don't bleed the system it will overheat. GL

 

My air bubble was so bad, that when i tried to "burp" the system, it wouldn't even pass the it. You can do the holes in the tstat, or you can drain the system and refill it properly.

 

the new thermo has two holes in it already so it should be able to let air bubbles out. anyother suggestions??? If i cant get it fixed today im going to have to take it to the shop and have them look at it.

Matt

 

Darn.

Was this a problem before you replaced your thermostat gasket? You may want to give a new radiator cap a shot, but I don't think it would effect your cooling system that much, never know though. If coolant isnt moving, its either the thermostat, water pump, or a really, really clogged radiator.

With your symptoms though, I can't help to think either the thermostat is bad or installed improperly, or their is an air pocket formed under the tstat, which shouldn't happen with it having holes in it.