The serpentine belt is used to transfer mechanical energy from the engine's drivetrain to peripheral components within the vehicle. Older vehicles relied on multiple belts to accomplish the same tasks.
The use of the serpentine belt makes basic maintenance of a vehicle less complex. Instead of having to remove multiple belts to replace a single worn components, the average vehicle owner can replace a single serpentine belt with little effort and no specialized tools.
If the belt fails, it can result in the complete loss of all peripheral functions. In most vehicles, this includes air conditioning, alternator, water pump and power steering. Loss of these components can be dangerous, which is why it is recommended that the serpentine belt be inspected regularly for fraying, cracking or signs of damage.
In some vehicles, failure of the serpentine belt can cause the engine to stop running to preserve function. This is especially true if the vehicle's water pump is driven by the serpentine belt. Ideally, a serpentine belt should last between 60 and 100 thousand miles before it needs replaced. When failure is imminent, belts begin to whine while the engine is running due to a loss of tension caused by the belt losing its elasticity.