alright, so i got a 2002 v6 vortec 4.3. it has been getting unsually hot really fast (hot as in getting up to 210 and alittle above 210degreesquickly). it completlety over heated when i took a trip on the freeway the other day.my heater is blowing cold air. it will blow hot air every once in awhile for about 3 - 5 seconds, then back to cold. when the heat does kick on, the temp will drop to normal.and i just replaced thethermostat. any ideas? water pump maybe? thanks!

 

almost sounds like a bad heater core..

 

Have you checked your coolant? I assume you've taken this important step one, but if you haven't it would be a cheap fix to your problem.

 

You must verify that the cooling system is full, there are no leaks, and all of the air is out of the system. Also, if you replaced your t-stat, it is a good time to replace your radiator cap. A weak radiator cap can cause overheating.

 

if you have air in the system it can get trapped in the heater core.. time for a flush...