2000 Ford F-150 how do I remover the fan belt tension pulley

If the tensioner wont release, then the entire unit will need to be repalced. Be sure you arent working on an idler pulley, they look just like the wheel on the tensioner but are solid mounted. Sometimes the threads are the opposite on the tensioner wheels (left tightens, right loosens). But again if the tensioner is stuck, replace it before it leaves you stuck somewhere