Revving keeps the air warm. I pulled the small return hose off the coolant jug and put it into an empty jug. When I rev the engine, coolant comes out the hose. When I let off, it stops. At first I thought water pump, but now I am not sure. Yesterday morning the temperature didn't reach 190, but it did later I the day.Does revving the engine keep the air warm? Its sounds like a thermostat/waterpump issue.