What is a Serpentine Belt?

Dan Cavallari

Take a look underneath your car and you will most likely find a belt or system of belts attached to pulleys on the front of your engine. If there is only one belt wound through several different pulleys, you are looking at a serpentine belt. The serpentine belt is different from other types of belt systems because the serpentine belt is one long, continuous belt that is connected to several different devices. Older systems employed the use of numerous belts to drive the devices in the engine compartment, but after the development of the serpentine belt in 1979, most cars began to use the system for efficiency and ease of use.

Alternators often rely on pulleys or belts to operate.
Alternators often rely on pulleys or belts to operate.

Peripheral devices such as the power steering pump, alternator, and air pump all connect to belt systems. In the past, two or three of these peripheral devices would be connected to each other, but not to all peripheral devices. Therefore, if one of the belts broke, the driver might be unaware of the loss of one device. Because the serpentine belt connects all the pulleys of peripheral devices, the driver will notice quickly if the belt breaks because all peripherals -- including power steering -- will immediately suffer or shut down entirely.

Automobile engines typically use pulley systems, such as those that work with the alternator, fans, water pumps, and timing gears.
Automobile engines typically use pulley systems, such as those that work with the alternator, fans, water pumps, and timing gears.

Serpentine belts are much easier to install than individual belts. There is usually one movable pulley putting tension on the serpentine belt, so replacing the belt involves simply loosening that pulley, removing the old belt, replacing it with a new serpentine belt, and tightening to the appropriate specifications. Older systems necessitated a mechanic to identify which belt was broken and work around other belts and engine components to replace the belt.

Serpentine belts are less prone to stretching and breakage than smaller and weaker individual belts. Tension is more equally distributed along the length of the belt, thereby reducing slippage and stretching. Because serpentine belts are typically longer, larger, and wider than individual belts, they tend to last longer and resist frequent breakage.

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