What does a timing belt do?
The timing belt, or cambelt, is a vital engine component with a key role to play in keeping your motor running smoothly. It ensures the top and bottom halves of your engine rotate precisely in time with each other.
Essentially, this ribbed rubber belt with teeth synchronises the crankshaft and camshaft’s rotation. It controls the sequencing and timing of the opening and closing of the valves on the cylinders in your engine to provide the right combustion.
Camshafts, made up of the main journals, the lobes (or bulges) and the ends, control the valves in the cylinder head. A rocker head takes the spinning motion of an overhead camshaft and turns it into the movement that opens and closes the valves.
Timing chains essentially perform the same function as cambelts but may be slightly noisier. The chains generally last as long as the vehicle (and generally require less frequent replacing), although the plastic guides they run over may not.
How often should a timing belt need replacing?
There’s no ‘one size fits all’ approach for how often to replace yours—a lot depends on your motor’s age and condition.
There’s also huge variation between manufacturers and different engines. So you might need a new belt after 4 years, or 6, or after driving 40,000 or 100,000 miles. Consult your car’s manual—most manufacturers’ recommendations are based on time passed or miles driven, depending on which elapses first.
However, we’d always suggest treating these recommendations as a maximum, and erring on the side of caution.
The law, vehicle regulations, and your MOT
The timing belt will not be examined at your car’s MOT, but the associated issues of running a car with a faulty timing belt can lead to severe engine damage, which can.
What causes a timing belt to stop working correctly?
Like most car parts, your timing belt will wear out eventually due to cracking, snapping or tearing. Timing belts are also unpredictable, with few warning signs of damage. (Although starting issues and noise may offer clues.) Driving your car infrequently, oil leaks and temperature changes, among other factors, can all play their part.
Symptoms of a malfunctioning timing belt
You hear unusual noises coming from the engine
If a grinding or squeaking noise is being emitted from your engine, it could be a malfunctioning timing belt.
The car won’t start
If your timing belt has broken, this can cause problems with your engine that lead to the vehicle not starting.