Many parts of a car's engine, including the alternator and power steering pulley, are connected by a serpentine belt. To replace one of the parts connected to the serpentine belt, the belt tensioner pulley has to be loosened and the belt removed. Loosening the tensioner pulley is accomplished by pulling it in a direction that gives slack to the serpentine belt. This action enables the belt to be removed and for replacement or repair of motor parts. Most tensioner pulleys require a standard ratchet for loosening.
Find the serpentine belt information sticker on the vehicle. This sticker will show the routing path and size of the serpentine belt. Sometimes these stickers also indicate what size socket or ratchet end is required to loosen the belt tensioner pulley. Take note of the socket required if indicated on the serpentine belt information sticker. If the sticker does not provide this information, find the belt tensioner pulley as labelled on the sticker. Inspect the belt tensioner pulley to see what size gap it has for a tool to fit in. If the gap is 1/2 wide and square, as is the case in many vehicles, a standard 1/2 inch ratchet will be sufficient.
Insert the appropriate tool into the gap in the centre of the belt tensioner pulley. This will provide the leverage needed to pull the belt tensioner forward and release pressure from the serpentine belt. If the gap is fitted for a 1/2-inch square, yet the ratchet end alone does not reach the gap, a ratchet extension bar may be helpful. Also, some vehicles require a star-shaped Torx bit to loosen the belt tensioner. While the pulley is being pulled forward, slide the serpentine belt off of any pulley it is connected to. Release the pressure from the belt tensioner pulley by removing the tool.
Inspect the pulley and belt while they are apart. Check the pulley for any cracks and wiggle it to see if it is loose. Belt tensioner pulleys should be tight when pulled horizontally, though they can give some slack when pulled in the direction that they operate. The serpentine belt should be free of excess splitting and should feel solid to to the touch. Replace any belts that have cracks or feel brittle when moved.
Many Ford vehicles require a less common Torx bit to loosen the belt tensioner pulley. These bits are often not included in small socket sets but can be purchased individually at auto parts stores.
Always use the correct tools when working on a vehicle. Though some belt tensioner pulleys may be movable by hand force alone, using the appropriate tool will reduce the risk of pinching a finger or other injury.