This tensioner pulley maintains the correct tension on the multi-ribbed belt within the drive system. It is mounted on a stationary bracket and uses a bearing to rotate freely as the belt passes over it. The pulley ensures the belt does not slip on the crankshaft, alternator, or other driven accessories. A seized or worn bearing will cause belt squeal, increased vibration, and eventual belt failure. The manufacturer machines the pulley face to the same width and groove profile as the original assembly, so the belt seats correctly and does not ride on the groove edges. When replacing, inspect the bracket for wear and torque the mounting bolt to the specification for the host engine.