There are two types of tensioner pulleys that provide the tension on an engine's accessory belt or belts. One type is self-adjusting; the other requires manual adjustment. The self-adjusting pulley is spring-loaded and provides its own tension. The other requires adjustment with a bolt that is located on the side, top or bottom of the pulley. Only the latter type of tensioner pulley may be altered.
Open the bonnet and secure it in place with the locking rod attachment.
Locate the manually adjustable tensioner pulley on the front of the engine. The pulley will be round with a bolt head in the middle of it and an adjustment bolt sticking out of the side, top or bottom of the pulley. The pulley is generally mounted to a bracket that is in turn attached to the alternator bracket or the power steering bracket.
Loosen the bolt head in the centre of the tensioner pulley with a ratchet and a socket by turning it counterclockwise.
Turn the adjustment bolt on the side, top or bottom of the pulley counterclockwise with the ratchet and socket until the accessory belt is loose enough to remove.
Tighten the tensioner pulley by turning the adjustment bolt clockwise with the ratchet and socket until the belt is tight. Tighten the bolt in the centre of the pulley with the ratchet and socket.
The self-adjusting tensioners are not designed to be adjusted because the spring loaded component inside of the pulley keeps the belt properly tensioned at all times.
Use caution when working around a hot engine to prevent any serious burns.