Many of today's engines use timing belts, but not all. Some engines use a timing chain and sprocket arrangement. A timing belt is a precision component with teeth that mesh exactly with its mating sprockets. Especially critical is uniformity of the teeth and their spacing. The belt's teeth are precision molded from a special rubber compound for good mesh and long life. The belt's inherent tensile (stretch-resistant) qualities come from high strength cords that run parallel with the direction of belt travel.
The timing belt maintains crankshaft-to-camshaft synchronization, keeping valve operation matched to piston position. On some engines, the belt also drives other components. These include the oil pump, water pump, and balance shafts.
Check your car's owner's manual for information on timing belt maintenance. Manufacturers generally recommend a certain mileage for belt replacement. If the timing belt is not replaced at the suggested interval, the belt could break, leaving you stranded and possibly causing major engine damage. If you're having the timing belt replaced, consider replacing other parts that may be accessed at the same time. The water pump, timing belt sprockets and tensioning pulleys are good examples. Check with a qualified service technician if you have questions about your car's needs for timing belt maintenance.