Driven by the crankshaft, the timing belt causes valves to open and close at the proper time keeping the engine in sync. If the timing belt is loose or improperly adjusted, it may "jump time" by skipping a tooth or more. This results in a loss of synchronization of the engine which is needed to maintain the mechanical integrity of the engine and also a loss of engine performance making a timing belt replacement an important part of a vehicle maintenance.
The timing belt is made from rubber and reinforced with fiber cords and naturally degrades over time. It should be replaced at scheduled intervals, which is usually every 60,000 to 90,000 miles. The intervals may vary depending upon the car manufacturer's recommendation. When the timing belt fails is could cause a non-interference engine which happens when the valves and pistons do not come into contact with each other or it could cause an interference engine which is where the pistons hit the valves causing major engine damage. In some cases, when the timing belt fails, the engine will simply stop running.replacing the belt will fix the problem.
A timing belt replacement involves removing the fan belts, pulleys, crankshaft pulley, and timing covers. Often times when replacing the timing belt a mechanic will inspect components inside the timing cover and, if needed, replaces oil seals, tensioners, and idler bearings. On certain engines, the water pump should be replaced at the same time as the timing.
Since a timing belt is an important part of a vehicle's operation, it is advised to follow the factory recommended vehicle maintenance schedule for how frequently a timing belt replacement is required. This factory recommendation must be adhered by to maintain the validity of your new car warranty and extended auto warranty, if applied. If mechanical breakdown occurs due to the lack of your car's maintenance of the timing belt, the warranty would not cover the car repair.