I have a 2004 mustang gt with a single turbo built motor etc. I just got it back on the road after it sat for years in a shed. It has a slight overheating issue and need some help figuring this out. When it first got up and running I didnt have a fan on it but never let it get hot enough to overheat. It overheated once driving it down the road a little ways. I put a better electric fan on it and it kept it around 195-200 degrees when cruising. If I turned the car off for around 5-10 minutes the heat soak would bring the temp up and the car would never cool back down. It has the thermostat that was in it when it was put up now which im assuming isnt working right. I have a new thermostat ready to go in it and when we filled it with antifreeze I only had one gallon and put the rest water. I havent had time to fool with it but am wondering if just changing the thermostat and putting antifreeze/coolant in it would solve the problem?