The serpentine belt tensioner applies tension to the serpentine belt by use of an internal spring; the spring pushes an arm equipped with a pulley that rides on the belt, holding tension on it to prevent the belt from coming off the vehicle on its own. The Ford Taurus tensioner is essentially the same as any other tensioner, with the exception of the specific measurements, which are engineered to meet the needs of the Taurus. If the tensioner spring breaks, the tensioner pulley's bearings fail or the tensioner becomes damaged some other way, you'll need to spend a half-hour replacing it.
Raise the hood and insert the belt tensioner tool into the side of the belt tensioner.
Move the tensioner to the side, using the tensioner tool, in order to release the tension from the pulley riding on the serpentine belt. Once the tensioner pulley is away from the belt, reach in with your other hand and move the belt to the side, out of the pulley's path.
Remove the belt tensioner tool and unbolt the tensioner body from the front of the engine using the socket set. In some model years, you may need to remove the idler pulley to get at one of the tensioner mounting bolts. The idler pulley can be removed by unbolting the fastener in the center of the pulley and then pulling the pulley out and away from the engine.
Lift the old tensioner out and position the new one in its place. Thread the mounting bolts back in by hand as far as you can and then tighten them down completely with the socket set. If you removed the idler pulley, put it back on now by threading the bolt in by hand and then tightening it with the socket set.
Reinsert the belt tensioner tool and move the new tensioner pulley out of the belt path. Reach down with your second hand and move the belt over the tensioner pulley and release the pressure on the tensioner by relaxing the tensioner tool. Remove the tensioner tool.
Start the engine and pay attention to how the belt travels for a few seconds. If the belt is wobbling or not fully seated on a pulley, shut the engine off and correct the belt travel by releasing tension with the tensioner tool and hand positioning the belt on the pulleys before trying again.
