Was out last night for awhile, just replaced the thermostat so wanted to test things out. Well the needle started creeping up and after about 2 hours of driving around fine it was nearly pegged. I pulled over and sure enough released enough steam that it looked like the car was on fire. The top rad hose felt like a rock there was so much pressure. The thermostat is a 160 degree stat and I didn't lose any coolant hardly. What are your thoughts? Maybe it's the waterpump?