driving to work this morning which is about 20 miles I stopped at the light half way to work and I noticed after a minute it starts blowing ice cold air and the temp reads all the way hot. then as I pull away it goes back to normal. next light it does it again. I checked the water at lunch and it looks full in radiator so I add some to the overflow tank. I drive 15 minutes and it heats up and down about 5 times but on the way back it runs normal the whole way. Everytime it shows hot the heater blows ice cold like it is low on water but it isn't low. Any ideas?

rhutson in NC

 

my dad had that happen a while back, then it just stopped doin it, he thought it was the radiator fan going out, but we never found out what it was after it stopped doing it.

 

Thermostat is sticking closed. Motor heats up because of no circulation. No hot water getting to your heater-core.
Change the Thermostat... My guess.

 

Sounds about right. You have a clog in your cooling system somewhere, most likely the tstat.