Several types of engine belts need to be replaced from time to time. Vehicles from 1990 and newer typically have a serpentine belt. The belt snakes around the pulleys located at the front of the engine (or the side of a transverse-mounted engine) and drives multiple accessories including the alternator, power steering pump and air conditioning compressor. If it is squeaking or worn, it could break, which would make the engine inoperable. Check it at 60,000 miles but change it before 100,000 miles. Older vehicles usually have separate belts for the water pump, alternator, radiator fan and air conditioning system, but when they break, you still may be able to get home. Finally, engine timing belts help to keep the camshaft and crankshaft in sync so that pistons and valves operate in sync. They typically last from 60,000 to 90,000 miles. A broken timing belt could result in engine damage and an expensive rebuild.