This tensioner pulley maintains the correct belt tension on the engine cooling fan drive. It is mounted on a pivot arm that presses against the belt, compensating for stretch and preventing slip at the fan hub. A worn pulley bearing produces a chirping or squealing noise as the belt oscillates, and the belt may begin to track off the pulley face. The pulley is manufactured to the same bore diameter and face width as the original component, so the existing pivot arm and mounting bolt can be reused without modification. When replacing, inspect the pivot arm bushing for wear and torque the center bolt to the specification for the host engine.