A timing belt controls the timing of the engine's valves. When a timing belt snaps, certain types of engines can be ruined. It is best to replace the timing belt when you have reached the number of miles your car manual recommends for a replacement, or when you see some symptoms signaling that the timing belt is going bad.
There are two different types of engines: interference and non-interference. If a timing belt snaps or slips on an interference engine, the engine will be badly damaged costing a small fortune in repairs. If a timing belt snaps on a non-interference engine, the engine will be damaged but will not cost as much in repairs as an interference engine.
Timing Belt vs. Timing Chain
1. Some cars come with a timing belt, but some come with a timing chain. A timing belt is made of rubber and is more apt to break than a timing chain. Some car makers recommend changing the timing belt every 120,000 km, while timing chains typically last the life of the car unless symptoms arise. Refer to your car manual to check the recommended mileage for changing your timing belt.
2. If your car fires more than a typical amount of exhaust, your timing belt could be worn out.
Difficult to Start
3. If your car has high mileage and is difficult to start, the timing belt could be going bad.
4. Older rubber timing belts degrade in hot temperatures and with exposure to motor oil. If your car runs hot and has a leaky engine, the life expectancy of your timing belt is lowered. Newer timing belts are made of heat-resistant materials and do not have this problem.
5. A working timing belt is perfectly timed with the valves and pistons. If the belt is going bad, the timing will be off, causing the car to shake.