BMW E53 Belts 

Your BMW's drive belts are wear items, and will degrade and crack over time. Don't wait until you have a belt failure... don't get stranded! Replacing your BMW's belts, such as the alternator belt, power steering belt, air conditioning AC belt, or serpentine belt is a low cost insurance policy to preventing a break down -- or worse, engine damage. We recommend checking your belts every 10,000 miles. If your belts have excessive cracks, dry rot, missing teeth and/or grooves, are cause noise, it's time for new ones.

While also inspecting your serpentine belts, also check for wear or resistance in the pulleys. The tensioner pulley and deflection pulley are the primary sources for belt squealing. The rubber-isolated pulleys can also break apart, leading to total belt failure. We sell the tensioner and deflection pulleys for the M50 engine family used in the E34, E36, E39, E46, X5, Z3, and Z4.