The serpentine belt in a car operates the water pump, which keeps engine temperature under control; the alternator, which charges the battery; power steering; and air conditioning. The serpentine belt gets its name from the way it winds around all the pulleys driven by the crankshaft, replacing the older V-belt system of using individual belts for individual accessories. This makes replacement easier, but when it breaks, everything it is wound around stops rotating. Many serpentine belt systems include a spring loaded pulley known as an automatic tensioner, which ensures that the belt is not too tight or too loose. It is recommended that these belts are replaced every 45,000-60,000 miles or when it becomes cracked, frayed, or glazed.

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