What happens if the timing belt breaks while the car is driving? Can the timing belt be replaced alone?

The timing belt belongs to the valve system of the automobile engine. It controls the intake and exhaust timing of the engine together with the valves and crankshaft. It is a very important component. The timing belt also needs to be replaced regularly. If it suddenly breaks while driving, it is likely to need a major repair.

What happens if the timing belt breaks while the car is driving?

If the timing belt breaks, first of all, the parts after the timing gear will stop moving, and the engine will definitely stop due to abnormal intake and exhaust. At the same time, due to the inertia of the flywheel, the crankshaft will still rotate a certain number of times, which will cause damage to the parts on this transmission path.

When the belt breaks, some valves must be in the open position, and when the piston rotates with the inertia of the flywheel, the piston and the valve will collide. There are two results:

If there is a rocker arm in the transmission system, the rocker arm will usually break first, which can protect the piston, valve and other cylinder components from damage, so the engine maintenance cost is lower.

If there is no rocker arm and the camshaft directly drives the valve to open, the valve will be bent or the piston will be damaged, which may cause serious damage to the engine cylinder and the engine may need to be replaced.

Can the timing belt be replaced alone?

The cost of replacing the timing belt and related accessories for general models is not very high. In order to prevent problems with the operation of tensioners and idlers, it is recommended to replace the related accessories together when replacing the timing belt regularly, which is relatively more cost-effective and worry-free.

The replacement cycle of the car timing belt can be checked in the maintenance manual. Usually, the replacement cycle of the timing belt is within 5 years or about 80,000 kilometers. Generally, when the timing belt needs to be replaced, other related accessories such as tensioner and idler will also be replaced. If the timing belt is replaced alone, the labor cost is the same, but the cost of other accessories is reduced, but it is not necessarily cost-effective.

The difficulty of replacing the timing belt may vary for different models. For example, the tensioner, water pump, and idler are bearing-type running parts. After a certain period of work, the bearing lacks lubrication, will have different degrees of wear, and the bearing may get stuck. At that time, the water tank, fan, generator, engine mounts, etc. need to be disassembled, which costs more money.

How Timing Belts Work

First, let's understand valve timing.

Valve timing refers to the correct moment when the valves open and close. The purpose is to make full use of the inertia of the airflow, let in as much fresh air as possible, and exhaust as much exhaust gas as possible, so that the engine can achieve good power.

The intake valve usually opens earlier than the top dead center of the intake stroke, and closes later than the bottom dead center of the intake stroke, so as to ensure as much intake as possible; the exhaust valve usually opens earlier than the bottom dead center of the exhaust stroke, and closes later than the top dead center of the exhaust stroke, so as to ensure as much exhaust as possible.

The mechanical transmission process of valve opening goes through crankshaft - timing belt - timing gear - camshaft - (rocker arm) - valve in sequence.