1994 Chevrolet Impala SS. Loan my car out. I was told that the serpentine belt broke and kept driving a few miles to get another belt from the auto part store. New serpentine belt was install and now I notice that my car will start to over heat when the car is not moving. When the car starts to move the temperature will drop. Any chance the the water pump got damage or air got in the system? There's a lot of air that builds up and I release from the bleeder valve that's on top of the thermostat. Thanks in advance.