Hello guys! I've recently purchased an 02' F250 SD with a 5.4 in it. The cooling system seems to get air bound on the engine side of the thermostat, which will then cause the engine to "overheat" and the heater to blow cold. I thought that I had a Head Gasket issue, but I'm not burning, leaking or losing any coolant. The only coolant I lose is when the system gets itself air bound and it forces coolant from the Degas bottle cap. I removed the air bleed check valve from the thermostat to allow any air to escape easier. This allows to drive the truck at least, still pushes coolant though. The pressure check of the system was great. The first check was done cold, held 17 lbs. for approx. 1/2 hr. When the engine was warm I had the same results. I started the engine and the pressure never built up pass 16psi. Now Im just wondering if I have a large air pocket caught in the heater core or something, and when the engine gets warm the air expands and forces the pressure to rise which then forces coolant from the cap. I have bled the system multiple times with the same results. The waterpump, thermostat, and fan clutch are all new. Please help.