How Serpentine Belts Work

Step 1 - A serpentine belt's function is to supply power to the steering system, water pump, air conditioner and alternator. When the serpentine belt fails it will almost always render the vehicle inoperable; power steering operation, alternator and water pump functions stop working. Learn more

Serpentine Belt

Step 2 - A serpentine belt is a normal service item that must be replaced when worn (glazed) or cracked.

Cracked Serpentine Belt

Step 3 - The tensioner automatically holds the proper tension on the belt so there is no need for re-tightening like in older models. If the belt is loose, the tensioner has failed or the wrong belt size has been installed. A tensioner should be about half way between its throw to hold proper tension on the belt. Learn more

Serpentine Belt Tensioner

Helpful Information

There are several names used to describe a serpentine belt, including: drive belt, poly-v belt, multi-rib, and micro-v belt. These belts are designed with several "v" grooves which provides better traction for the drive and components pulleys than traditional single "v" belts. When the belt tensioner starts to fail it will allow the serpentine belt to get misaligned causing the belt to come off, the belt can be damaged in this event.

On rare occasions, an engine can buck or jerk on start up which can suddenly cause a belt to jump out of place.

Typically most people are able to replace a serpentine belt with basic automotive tools and repair knowledge.


Use a flashlight to perform a complete visual inspection of the serpentine belt, look for fraying, cracking or large pieces missing. When replacing the belt inspect all belt pulleys for damage or rough spots that will effect the new belt. Regular replacement of this belt will help prevent breakdowns.

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