What Is the Purpose of a Serpentine Belt?

by William Norman
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A car engine's serpentine belt, also known as an accessories belt or drive belt, powers individual systems external to the vehicle's engine, such as the compressor, air conditioner, alternator and other systems. Some cars use more than one serpentine belt for this purpose, according to Samarins, dividing the drive tasks among two or more belts. The critical functions performed by the serpentine belt make it an essential part of the engine system, making regular inspection and maintenance of the belt a crucial step in keeping the car operational.


The serpentine belt plays a major role in a car's electrical charging system. It attaches to pulleys on the car's alternator to provide power to this unit, which in turn delivers electricity to the car's battery so it can build and hold an electrical charge. In this capacity, the serpentine belt replaces individual "V" belts that serve an alternator or other components exclusively, since a single belt means simpler replacement and fewer parts that can fail.


The serpentine belt powers several mechanical components on a car, according to Auto Upkeep. The power steering system, for instance, depends on power delivered to it by the serpentine belt. The car's cooling system also contains several components powered by the serpentine belt, including the water pump, radiator fan and air conditioner compressor.


The serpentine belt can only fulfill its purpose if held under the correct tension. A mechanical device called a tensioner applies just the right amount of tension to the belt to keep the belt running at the proper speed and resistance to perform its functions. A loose serpentine belt will slip, resulting in reduced efficiency and, in some cases, an annoying whistling noise that signals the need for a replacement belt, according to AA1Car. Some older cars require manual tensioner adjustment, while many more modern cars include tensioners that adjust themselves automatically.


The serpentine belt provides many of the basic functions a car needs to operate. A car simply cannot run without a working serpentine belt. If the belt breaks or works itself off of its pulley system during operation, the car will immediately lose its ability to cool the engine, charge the battery, engage the automatic steering or run the air conditioner.


Keeping the serpentine belt system in optimum condition can ensure that the belt continues to perform its vital role in the car's operation. Hard-to-spot weaknesses can creep into the belts through natural wear or exposure to engine fluids. Most serpentine belts can deliver at 50,000 to 60,000 miles' worth of reliable performance, but changing the belt at around this interval will help car owners avoid eventual belt failure and the resulting car breakdown. The pulleys and tensioner must also perform within specifications to ensure a lengthy belt life, so owners should have these parts checked at the same time.

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