Serpentine Belt

What it does

The serpentine belt is a long, flat, ribbed rubber belt that snakes around a series of pulleys at the front of the engine — powering the alternator (electricity), power steering pump (steering), water pump (cooling), and air conditioning compressor, all from the engine's rotation. It's called 'serpentine' because of how it winds through all these pulleys like a snake. When it wears, it squeals on startup. When it breaks, all those systems stop instantly — the engine overheats, you lose power steering, and the battery drains. A broken serpentine belt can also damage other components if it flails around.