Whether your engine has a timing belt or timing chain decides your maintenance. A belt is replaced on a schedule by age and mileage, while a chain is designed to last much longer but can stretch. On an interference engine, a snapped belt can mean serious internal damage.
The timing belt or chain keeps the crankshaft and camshafts turning in exact relationship. If that relationship is lost, the valves and pistons can occupy the same space at the same moment, and on most modern engines that means serious internal damage.
The difference that matters
A timing belt is rubber reinforced with fiber, runs dry, and has a defined replacement interval in miles or years, whichever comes first. A timing chain is metal, runs in engine oil, and is generally designed to last the life of the engine. Belts are a scheduled job; chains are a condition-based one.
Interference engines
Most modern engines are interference designs, meaning the valves and pistons share space at different points in the cycle. If the timing is lost, they meet. The result is bent valves and frequently worse, and the repair often costs more than the car is worth. Non-interference engines simply stop, which is inconvenient rather than catastrophic.
Why the years matter as much as the miles
Rubber ages whether the car is driven or not. A low-mileage city car that is seven years old can be due on time even though it is nowhere near the mileage figure. This is the one that catches people out, because the odometer suggests there is plenty left.
What is replaced with it
The tensioner and idler pulleys, and usually the water pump if it is belt driven, because the labor to reach it is already being paid for. Replacing a belt and leaving a fifteen year old water pump behind it is doing the job twice.
Chains are not maintenance free
A chain stretches over a long life, and a stretched chain rattles on start-up before the oil pressure builds. Chains also depend entirely on clean oil, so a car with a history of missed oil changes can wear one early.
Find out which you have
It is a straightforward thing to check, and worth knowing. See car maintenance or ask us.
Engine repair at Midtown Center Auto Repair.
Timing Belt or Timing Chain: Questions
How do I know if my car has a timing belt or timing chain?
Your owner's manual will tell you whether your engine has a timing belt or timing chain; a listed replacement interval means a belt. We can also check it for you.
What is an interference engine?
One where the valves and pistons share space, so if the timing is lost they collide, causing major damage.
What else is replaced with a timing belt?
Often the tensioner, idler pulleys and, where it is belt-driven, the water pump, since the labor overlaps.
