Here's the case. I was driving home the other day and everything was ok. Then the 6.2 started to overheat. I stopped to let it cool down and then added some water to make it home. It would get hot and then cool down, get hot cooldown. So I figured my thermostat was going bad. I pulled the thermostat to get home. I had been driving it a couple days back and forth to work so it never got hot (1 1/2 miles). I got a good Stant HD thermostat and put it in. I just can't seem to get the 195 degree thermostat to open in the 6.2. I pulled it out and placed in a pot, heated the water to make sure the stat was opeming. I didn't have a themometer to see what temp it was opening but it was opening when the water was heated. I placed it back in the 6.2, but i still can't seem to get the thermostat to open. I thought I might have an air pocket keeping the water from the stat and did everything to get it to work, still no luck. I was told I may have a cracked head, blown head gasket and other deals. I'm not convinced. The 6.2 runs smoothly, no evidence of water from the exhaust pipes, no water in the oil, No leaks from anywhere. I'm really confused right now. Amyone want to make a suggestion what i might look for or any suggestions. Anything would be greatly appreciated.