Since the late 1990s, automotive manufacturers have phased out Neoprene serpentine belts and are now installing ethylene propylene diene monomer (EPDM) belts on new models.
While it's hard to tell neoprene and EPDM belts apart visually, EPDM belts far outlast and outperform their predecessors. Neoprene belts have a life expectancy of 50-60K miles, and as they wear out, cracks and chunk-outs will occur. EPDM belts rarely show these symptoms, even at very high mileage.
Belt wear after 100,000 miles
As EPDM belts age, they gradually lose rubber material similar to the way a vehicle’s tires wear out. Over a period of 100,000 miles, a belt can lose up to 10% of its rib material. While this may not seem like a lot, the consequences can be significant.
When EPDM serpentine belts lose material in the valleys of the ribs, the space between the ribs widens without the ribs getting shorter. As more material is lost, the pulleys ride deeper into the belt valleys resulting in slip, noise, and hydroplaning.
With sufficient material loss, the pulley ribs “bottom out” in the valleys and ride on the belt cord. This reduces the surface contact on the valley sides where the traction is generated. Wear also increases the effective belt length, lowering the tension in the system, which also reduces traction.
Belt wear problems that reduce performance of the Accessory Belt Drive System (ABDS) include:
If your serpentine belt exhibits one or more of the symptoms depicted, it needs to be replaced.