ok guys same problem with a new twist...lol I changed my radiator out the weekend and put a new cap on and new coolant also..now I still have the sound of water running when moving but now the heat works sometimes...if I sit with the truck running and the fan off then turn the fan on it blows hot or warm air while driving it blows just enough to defrost the windshield ....now could this be from the air pocket some of the guys was talking about??? its just crazy how this stuff works now days...