This belt tensioner maintains the correct drive-belt tension on the engine accessory drive system. It is located on the front of the engine, where it applies a constant force to the belt span between the crankshaft pulley and the alternator or fan hub. A worn tensioner allows belt slip, which reduces alternator output and coolant pump speed, leading to undercharging or overheating. The tensioner is an original-manufacture component, machined to the same pivot-bore tolerance as the original assembly so no bushing shimming is required during installation. When replacing, ensure the belt routing matches the original path and that the tensioner arm moves freely through its full arc before tightening the mounting bolt to the specified torque.