Timing belt - what is it and why

In the instruction manual for any car, the manufacturer indicates the frequency of scheduled maintenance of the vehicle. In addition to replacing technical fluids and other consumables, each car owner should pay attention to the planned replacement of the timing belt.

Consider what function the timing belt performs in the car, when it needs to be changed, what happens when it breaks and how to choose this element correctly.

Why is there a timing belt in a car?

An internal combustion engine operating in four-stroke mode is equipped with an extremely important mechanism that opens the intake and exhaust valves at the right time. They are responsible for the supply of a fresh portion of the air-fuel mixture and the removal of exhaust gases.

In order for the valves to open at the moment when the piston of a particular cylinder performs an intake and exhaust stroke, synchronization of the camshaft and crankshaft is required. This will allow the valves to always open at the right moment, regardless of the crankshaft speed.

To synchronize the rotation of the crankshaft and camshafts, you need timing belt. Without a gas distribution mechanism, a four-stroke engine will not work, since the cylinders will not be able to fill the required amount of air-fuel mixture in a timely manner, and the exhaust gases will not be removed in time.

Due to the presence of the timing belt, the torque is transmitted from the crankshaft to the camshaft, pump and, depending on the design of the engine, to other attachments (for example, to a generator).

How to know when it's time to change the belt

Since mechanical force is transmitted through the timing belt, and the crankshaft speed is often high, this motor element wears out over time. Sooner or later, every car owner will face the need to replace the timing belt.

The interval of this procedure is influenced by such factors:

• Working resource;
• Violation of the rules of installation and maintenance;
• Motor breakdowns;
• Improper operation of the vehicle, for example, if you often start the engine from a pusher or tug and make mistakes in this procedure.

More often, the belt is replaced after a certain period of time or if there are malfunctions of the power unit. 

Degree of wear

Any part that is subjected to mechanical stress is bound to wear out and therefore needs to be replaced. The same goes for the timing belt. Only its wear is accelerated by breakdowns in the motor or improper operation of the vehicle.

If we talk about engine malfunctions, then the wedge of tension bearings, violation of the degree of tension (a loosely tensioned belt will slip, and an overtightened one will experience increased load) and other factors.

Sometimes the driver himself can cause premature wear and tear of the belt. As already mentioned, if the car does not start by itself, some drivers do not try to fix this problem faster, but continue to torment the car by starting from a pusher or tug. This often happens with a fast discharge or a weak battery.

Car mileage

To prevent a timing belt break, car manufacturers indicate at what interval it is necessary to change this element, even if it looks intact on the outside. The reason is that due to the presence of microcracks, the part will wear out faster.

If the driver ignores the belt replacement schedule set by the manufacturer, then at the most inopportune moment he will be faced with the need to adjust the gas distribution mechanism due to a broken belt. In the worst case, the car owner will have to spend money on a major overhaul of the motor (some types of pistons hit the valves when the belt breaks, because of which these parts become unusable and the motor needs to be sorted out).

Depending on the type of motor, the timing belt has its own working life. For example, brands such as Audi, Renault, Honda establish a belt replacement schedule every 120 thousand kilometers. For BMW, Volkswagen, Nissan, Mazda, this period is set at around 95, and Hyundai recommends changing the belt after 75 km. So it is necessary to navigate the frequency of replacement in accordance with the manufacturer's recommendations, and not with what a motorist from a neighboring garage advises.

What happens if the belt breaks

In many power units, pistons have special recesses. If the timing belt breaks in such engines, there will be no critical breakdowns, except for the need to adjust the valve timing. Since the valves in the motor must open at the right moment, a broken belt always leads to a complete stop of the motor.

Since notched pistons reduce the efficiency of the power unit, some manufacturers install even pistons. In such engines, a break in the timing belt leads to a meeting of the pistons with the valves.

As a result, the valves are bent, and in some cases the pistons are also seriously damaged. Even less common are situations where a break in the drive belt leads to breakage of the camshaft pastel or damage to the cylinder block.

To prevent such problems, each driver needs to pay attention to the following signs indicating the need to replace the belt:

1. Formation of cracks and traces of belt wear. If this element is protected by a casing (in most cars it is), then periodically it is necessary to remove it in order to conduct a visual inspection of the part.
2. Resource. Even if the vehicle has not completed the mileage specified in the owner's manual, the belt may still need to be replaced if there are no visible signs of wear. The belt is made of rubber, and this material has its own shelf life, especially under mechanical stress. Therefore, after 7-8 years of operation, it is better to replace the belt without waiting for it to wear out.
3. Unstable motor operation. This can be caused by belt slippage on the shaft pulley. Because of this, the valve timing is confused, and ignition may not occur correctly. The engine may start poorly, troit, it may shake. With several teeth slipping, valves and pistons can be damaged if they meet while the engine is running.
4. Plentiful smoke from the exhaust pipe. This is not always due to a malfunction in the gas distribution mechanism, but if the valve timing shifts, then the air-fuel mixture may burn poorly. If a catalyst is installed in the car, it will quickly fail due to the critical temperatures that occur when unburned fuel burns out in the exhaust system.
5. Extraneous sounds. When the driver hears strong clicks that are cyclical in nature and increase with increasing speed, it is worth looking to see if the belt has begun to collapse. The reason for such sounds and the engine compartment may be a worn bearing of a water pump or generator.
6. Belt oil. Rubber quickly breaks down on contact with petroleum products. For this reason, if traces of oil are found on the belt, it is necessary to eliminate the leakage of lubricant and be sure to replace the belt.
7. When starting the engine, the starter works, but the engine does not even “grab”. Most likely, this is a symptom of a broken belt.

How to choose and replace a belt

Since the stable operation of the motor depends on the quality of the drive belt, it is recommended to purchase the original version. Although such spare parts are more expensive than analogues from other manufacturers, when using the original, you can be sure of the reliability of the part, as well as that it will serve its due period (if the operating conditions are not violated).

If the belt part number for a particular motor is unknown, then the search can be performed by the VIN code. By symbols and numbers in this number indicates the type of engine, the date of manufacture of the vehicle, and so on. We are interested in the type of engine, not the model of the car. The reason is that in different years of production and in different trim levels, the same car model can be equipped with different motors, for which their own timing belts rely.

For some motorists, it is too difficult to find the right part on their own. In this case, you can use the help of a seller in an auto parts store. The main thing is to tell him the production date, model and brand of your car and, if possible, the type of engine.

When choosing a belt yourself, you should make sure that the new part meets the technical specifications (has the right length, width, number of teeth, their shape and pitch). Belt replacement should be done by a professional. In this case, it will be possible to avoid mistakes when installing the belt and it will serve the entire period assigned to it.