Several months ago I had a new AC installed in my 67 mustang. It worked great and blew cold. I had the car in a repair shop to get the carb overhauled. They told me they also had to replace the water pump gasket. When I picked up the vehicle and was driving it home, the AC blew cold air for about the first 5 or 10 minutes and after that, the fan was working but the air was not cold. It was blowing warm air. My oil pressure gauge was also on hot, like way past hot. Any idea whatt caused these two issues after they replaced the water pump gasket?? Did the repair shop mess up something??