My Mazda B2500 recently overheated leading to a new radiator and thermostat. After installing them and removing any air I have noticed that even after a half hour drive the bottom radiator hose is cold. Although the temp gauge is normal I feel something is wrong with the coolant flow but can't figure it out. The thermostat has been tested and sits at the end of the bottom hose, and the heater is working ok. I ran the engine without the therm and the bottom hose did warm up as it should. Any help would be appreciated.