Originally Posted by tonyford

Could it be: 1. A long shot, I bought a defective thermostat and it is still staying open.
2. The temperature sending unit has gone bad, very improbable since it does register the correct temperature when truck is moving down the highway.
3. The coolant is spent, again unlikely, it has been in the engine only for about 3 years and still looks clean and green.
4. Have to have a cylinder pressure check to determine actually if the head gasket is really blown or not, which I doubt..