Diagram of how to install a serpentine belt on a 2001 BMW 325i?

To install a serpentine belt on a 2001 BMW 325i, first, locate the tensioner pulley and use a wrench to rotate it counterclockwise to relieve tension on the belt. Remove the old belt and refer to the belt routing diagram, usually found on a sticker in the engine compartment or in the vehicle's manual. Thread the new belt around the pulleys according to the diagram, ensuring it sits properly in the grooves. Finally, release the tensioner to apply tension to the new belt.