On my way to meet up with a group to cruise to a car cruise in Saturday, I stop at this red light after driving non-stop from my house (about 40 miles). Soon as I stop, steam starts to roll out of the engine bay. So I pull into the parking lot and open the hood. The factory temp gauge does not show the motor to be over heating. I assume that I over filled the tank when I put on a new radiator cap and it was going everywhere. So, I drive from there (Knoxville, TN) to Somerset, KY (about 130 miles) non stop from speeds around 55-75mph the whole way. As soon as I come to a stop to a parking lot in Somerset, the needle on the temp pegs out but no steam. I park the car and open the hood. Once again the overflow tank is full. I figure it vapor locked and I let out some of the extra water and let the car cool off. I leave Somerset, KY to London, KY (35 miles or so) to get gas, and long story short, drive at 60mph whole way, slow down to a stop, needle pegs again. Car does the same thing from London, KY and when I pull into my driveway in Kingston, TN (about 180 miles). I'm going to replace the T-stat, temp sender and flush the system in a day or so. Anyone else have an idea on what could be causing this? I have a manual fan switch installed and the fan was working.