Serpentine Belt

📖 YOUCANIC Automotive Glossary

The serpentine belt (also called the drive belt or accessory belt) is a single continuous ribbed belt that wraps around multiple pulleys to drive engine accessories from the crankshaft pulley — including the alternator, power steering pump, A/C compressor, water pump (on some engines), and air injection pump. The belt follows a serpentine path (hence the name) around all pulleys with a spring-loaded automatic tensioner maintaining correct tension. Modern serpentine belts use EPDM rubber that wears differently than older neoprene belts — rather than cracking visibly, EPDM belts gradually lose rib material, reducing grip.

Belt failure symptoms include squealing noise (especially at startup or during A/C engagement — indicating slip from wear, contamination, or weak tensioner), multiple accessory failures simultaneously (belt broke), overheating (water pump stopped), no charging (alternator stopped), and heavy steering (power steering pump stopped). Inspect the belt by checking rib depth with a belt wear gauge — EPDM belts should be replaced when rib depth falls below the gauge threshold, typically every 60,000-100,000 miles. Always replace the belt tensioner when replacing the belt, as a weak tensioner is the most common cause of belt squeal and premature belt wear.