1995 Ford Mustang

First, does the engine miss or stumble upon initial start-up? This could be an indication of a faulty head gasket allowing coolant into the cylinders on shut down and allowing combution gases to enter the cooling system during running, effectively super-heating the system. Is the oil cloudy and milky? This is a solid indication of a blown head gasket. If you have passed these tests, check or replace the radiator cap, you system may not be pressurizing, as coolant escapes at 212 deg. F, the engine sensors will not recognize the true temps. And not turn on the coolant fans, as well, a sensor that is air-locked, (not surrounded by coolant as intended) will not allow for electric fan operation. Sometimes the hardest problems go all the way back to the basics, this cooling system must be pressurized to operate properly.