How do you install serpentine belt on a 318i BMW?

To install the serpentine belt on a BMW 318i, first, make sure the engine is off and cool. Locate the belt routing diagram, often found on a sticker near the engine bay or in the owner’s manual. Use a wrench to relieve tension on the tensioner pulley, then slide the old belt off and route the new belt according to the diagram, ensuring it sits correctly in all grooves. Finally, release the tensioner to secure the belt in place and double-check the alignment before starting the engine.