A serpentine belt is a peripheral part in your car which enables the internal combustion engine to function effectively. It is closely linked to a host of important features in your vehicle including the power steering pump, air pump, alternator, air conditioning compressor, and water pump. Designed in a long continuous style, it is the force behind many of these overlooked parts of your car. Guiding the belt as it moves is usually a belt tensioner or idler pulley. Like all parts in a car, the serpentine belt will need replacing at some point in time. Every 40,000 to 70,000 miles is a good rule of thumb to follow. Upon closer inspection, it should be obvious when the serpentine belt needs replacing as you will see it becoming frayed or cracked.