I have an 03 f350. I just replaced the water pump as the old one was leaking. After Changing the pump, I flushed the cooling system several times then switched over to red elc coolant. The problem I'm having now is, the upper radiator hose is full of air, I've driven it several times and the air doesn't come out. I'm wondering if the thermostat may be bad? It doesn't get over 200 when driving.