Did the valve bend when the timing belt broke: how to determine for yourself?

Continuous improvement of the internal combustion engine in order to increase efficiency and increase fuel efficiency has forced engineers to seriously redesign the design of modern diesel and gasoline engines. The changes also affected the piston group device and the combustion chamber. These modifications were made for the most efficient filling of cylinders and their quality ventilation, ie obtaining improved gas exchange.

We also recommend reading the article about it, what is the system of changing the phases of gas distribution. In this article you will learn about it, what varieties of these solutions are installed on different engines, as well as the principles of operation and design features of such systems.

If in the early stages of development the most common was the engine with two valves per cylinder (1 intake and 1 exhaust valve), today there is an increase in the number of valves per cylinder. Such changes are well illustrated by the most common version of the four-cylinder car engine. Previously, such motors were often 8-valve, with one camshaft. Today, such a unit is often a 16-valve version with two camshafts (for inlet and outlet valves), can be equipped with a system of changing the phases of gas distribution, etc.. d.

Timing Belt / Chain Break: main reasons

If we compare modern motors with their predecessors, today engines have more power and less life. As for the problem of valve bending, the distance from the piston to the valve is minimal in order to achieve greater recoil from the motor. Even a slightly open valve wicks when lifting the piston in TDC. It turns out, various technical innovations in engine construction did not affect the well-known problem, which is inherent in the vast majority of engines, regardless of engine type and manufacturer. We are talking about bending valves when the drive belt or timing chain breaks.

An important rule during the operation of the car is to monitor the condition of the timing belt and its timely replacement. There should be no bundles on the belt, cracks or other defects. It is also not allowed to get different technical liquids on its surface. The appearance of a squeak, creaking and other extraneous sounds requires the owner to check the tension and condition of the timing belt, as well as tension and other rollers.

To answer the question, when you need to change the timing belt, it is necessary to study the operating instructions for a particular car. Most often on new cars the belt changes through 60 thousand. kilometers traveled or through 2-3 years (depending on, which will come sooner). The planned replacement of the original belt involves the subsequent replacement of each 50 thousand. km. It is advisable to choose non-original belts with care and change each one 40 thousand. km

Now a few words about the chain drive. The timing chain requires less attention, since the replacement of the circuit on average is required once in 150-200 thousand. km. and more. It is necessary to monitor the tension of the chain, the condition of the tensioner and sedative chain. Increased noise during engine operation, the appearance of a metal rattle and other signs will indicate the need for immediate verification of these elements.

We also recommend reading the article about it, that can whistle under the hood in the cold. In this article you will learn about the possible causes of squeaking and squeaking, as well as ways to identify and troubleshoot.

so, let's go back to a less reliable belt compared to the chain. The timing belt is often torn for the following reasons:

• belt wear as a result of prolonged use or use of low quality products;
• jamming of the pump (water pump);
• wedge of the crankshaft of the camshaft;
• malfunction of the tension roller, jamming of timing rollers;
• destruction of a timing belt as a result of hit on its surface of engine oil;
• mechanical damage after contact with the sharp edges of the timing belt drive, camshaft gear;

Why bend the valve when the belt or timing chain breaks

Despite the refinement, the general traditional principle of operation of the timing belt and the valve mechanism of the engine remains unchanged. As you know, lifting the piston in TDC (top dead center) means, that at the specified moment the inlet and outlet valves are closed. This is necessary to create pressure and seal the combustion chamber.

If the timing belt breaks, then the valve simply does not have time to close, which means their collision with the rising piston. When the timing belt breaks, the camshafts stop immediately. This immediate stop occurs for two reasons:

• as the driving force from a belt or a chain disappears;
• on the cams of the camshaft have a decelerating effect of the return springs;

As for the crankshaft, this element of KShM continues to rotate by inertia. The inertial rotation of the shaft does not depend on that, in what gear and at what speed the car was moving, at what speed the engine was running, etc.. d. The flywheel still turns the crankshaft. In other words, if the timing belt has broken, then the timing mechanism stops immediately and the valves remain open, while the crankshaft continues to rotate and the movable pistons hit the valves open at this time.

The result of the breakage of the belt is that, that the piston meets the valves, after which the valves bend immediately. The valve stem often bends, although sometimes various deformations of the valve plate are also possible. Damage to the piston itself is less common, which are also the result of belt breakage and valve bending.

Engineers and automakers are well aware of this problem. To prevent the consequences of breakage of the timing belt / chain in some old internal combustion engines on the piston were made special grooves under the valve. These grooves actually provided the necessary free space, which allowed the open valves not to collide with the moving up piston. In such motors after break of the drive of the valve did not bend.

Modern engines also have characteristic notches on the piston. It is worth noting, that these grooves avoid the risk of damaging the valve on a running engine. When the timing belt breaks on such motors, these grooves do not save from bending the valves, that is, the valve is still wicked even in the presence of special recesses on the piston.

On which engines bends the valve: how to find out

Due to the seriousness of this problem and the high cost of further repairs, many motorists are concerned about the issue, how to find out, wicks or does not bend on the valve motor when the timing belt breaks. To learn more and determine, whether the valve is bent on a particular engine, you can use the following recommendations:

1. Examine in detail the technical documentation for the engine from the manufacturer. Let's add, that conducting a visual inspection, as well as various data from the tables still do not give 100% confidence, that at break of a drive belt of the valve do not bend. It is also not recommended to blindly trust statements on profile autoforums or rely on information from other more or less authoritative sources. In other words, the authenticity of any data must be questioned and re-examined.
2. Another way is the so-called "physical" check, which allows you to find out for yourself, bend or valve. This method allows you to determine the probability of bending valves, ie confirm or deny the possibility of contact of the valve with the piston.

For, to find out, oppresses or does not oppress the valve, you will need to remove the timing belt. Next, the piston in the first cylinder is set to the TDC position, after which the camshaft of the timing mechanism is rotated by 720 degrees. If in the process of turning the camshaft there is no stop, then it is necessary to carry out a similar test by alternately raising the TDC pistons in all other internal combustion engine cylinders. If the camshaft does not rest anywhere, then there is a high probability, that on the given engine of the valve at a belt breakage does not bend.

As for various technical information, which is shown in the tables, as well as referring to the experience of car mechanics and ordinary drivers, summary data allow to note:

• most valves do not bend on simple 8-valve engines;
• usually the valve bends on 16 - valve and 20-valve engines;
• the valve bends on almost all diesel engines;
• valve bending occurs on most motors in the event of a break in the timing chain, that is, on timing chain engines;
• valves are usually bent on the engines of small cars with a displacement of 1.1 to 1.4 liters;