Coolant looked good and was the proper color absent any oil or transmission fluid. I did burp the system. I am a welder for the railroad and havent had a chance to do a check of the temp on the radiator yet. I bought the t-stat at advance auto parts. The part that is baffling me as that as stated before the D has not overheated or even come close to overheating since I have been doing city driving here in Houston. Only on the highway when there is prolonged driving in hot temps (over 75 degrees so far). This is starting to drive me crazy. I love my D and really want to keep it but the expense that it is looking like it is going to be too much. I may have to trade her in but I really dont want to. Please Help guys.

 

Yes I did use 50/50 mix.

 

You need to take this to a shop then sorry to say, Something isn't right. They can verify a bad head gasket by a hydacarbon test.