A timing belt is a toothed belt which keeps the camshaft(s) in time or sequence with the crankshaft of the engine. Timing belts all have a scheduled interval since they wear out and can break. At the very least, a broken timing belt means an engine that does not run. In some cases, however, a broken timing belt also will damage the valves and possibly the pistons, causing your repair bill to triple or more.
The reason for this is simple - to achieve better performance, small engines often do not allow enough clearance for pistons if the valves get out of time. This is known as an interference engine. If you have a vehicle with an interference engine, it is especially crucial to replace the timing belt at recommended intervals to avoid a major repair bill. An ounce of prevention is worth a pound of cure. Even if you don’t have an interference engine, a broken belt means a tow bill and the inconvenience of an unexpected repair.
Depending on the mileage, we frequently recommend replacing related parts during the timing belt work since there is so much overlap in labor. Many water pumps are driven by the timing belt or at least not accessible without removing the belt, so when the timing belt is replaced it is wise to replace the water pump at the same time. The same goes for front engine seals and sometimes idler pulleys and timing belt tensioners.