Home Rack Kinked valve in the engine: causes and effects. Valve bending: what are the reasons and how to prevent What kind of engine valve bending

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Kinked valve in the engine: causes and effects. Valve bending: what are the reasons and how to prevent What kind of engine valve bending

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

If in the early stages of development the most common engine was with two valves per cylinder (1 inlet 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 automobile with four cylinders. Previously, such motors were often 8-valve, with one. Today, such a unit is often a 16-valve version with two camshafts (for intake and exhaust valves), it can be equipped with a variable valve timing system, etc.

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Broken timing belt / chain: main causes

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

An important rule during the operation of the car is to monitor the condition of the timing belt and its timely replacement. The belt must be free of delamination, cracks or other defects. Also, it is not allowed to get various technical liquids on its surface. The appearance of a squeak, squeak and other extraneous sounds will require the owner to check the tension and condition, as well as the tension and other rollers.

To answer the question when you need to change the timing belt, you need to study the operating instructions for a particular car. Often, on new cars, the belt changes after 60 thousand kilometers traveled or after 2-3 years (whichever comes first). A planned replacement with an original belt involves the next replacement every 50 thousand km. It is advisable to choose non-original belts with care and change every 40 thousand km.

Now a few words about the chain drive. The timing chain requires less attention, since the replacement of the chain is, on average, necessary once every 150-200 thousand km. and more. In this case, it is necessary to monitor the chain tension, the condition of the tensioner and the chain damper. Increased noise during engine operation, the appearance of a metallic clang and other signs will indicate the need for immediate verification of these elements.

So, back to the less reliable belt in comparison with the chain. The timing belt most often breaks for the following reasons:

belt wear as a result of prolonged use or the use of a poor quality product;
jamming (water pump);
wedging of the crankshaft, camshaft;
malfunction of the tension roller, jamming of the timing rollers;
destruction of the timing belt as a result of engine oil getting on its surface;
mechanical damage after contact with sharp edges, camshaft gears;

Why do the valves bend when a belt or timing chain breaks

Despite the improvements, the general traditional principle of the timing and valve train of the engine remains unchanged. As you know, raising the piston at TDC (top dead center) means that at the specified moment the valves are also closed. This is necessary to create pressure and seal the combustion chamber.

If the timing belt breaks, then the valves simply do not have time to close, which means they collide with the rising piston. When the timing belt breaks, the camshafts stop immediately. This immediate stop occurs for two reasons:

since the driving force from the belt or chain disappears;
the camshaft cams themselves are retarded by return springs;

As for the crankshaft, this element continues to rotate by inertia. The inertial rotation of the shaft does not depend on what gear and at what speed the car was moving, at what speed the engine was running, etc. turns the crankshaft anyway. In other words, if the timing belt is cut off, then the gas distribution mechanism immediately stops and the valves remain open, while the crankshaft continues to rotate and the moving pistons hit the open valves at this time.

The result of a broken belt is that the piston meets the valves, after which the valves are immediately bent. The valve stem is often bent, although sometimes various deformations of the valve disc are also possible. Less commonly, damage to the piston itself can be found, which is also a consequence of a belt break and bending of the valves.

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

Modern engines also have distinctive piston notches. It should be noted that these grooves avoid the risk of damaging the valve while the engine is running. If the timing belt breaks on such motors, these grooves do not save from bending the valves, that is, the valve still bends even if there are special grooves on the piston.

On which engines the valve bends: how to find out

Due to the severity of this problem and the high cost of subsequent repairs, many motorists are concerned about the question of how to find out if the valve motor is bending or not bending when the timing belt breaks. To more accurately find out and determine if the valves bend on a particular engine, you can use the following recommendations:

Study in detail the technical documentation for the engine from the manufacturer. We add that a visual inspection, as well as various data from the tables, still do not give 100% certainty that when the drive belt breaks, the valve does not bend. It is also not recommended to blindly trust the statements on the specialized auto forums or rely on information from other more or less authoritative sources. In other words, the validity of any data must be questioned and rechecked.
Another method is the so-called "physical" check, which allows you to find out yourself if the valves are bent. This method allows you to determine the likelihood of valve bending, that is, to confirm or deny the possibility of contact between the valve and the piston.

In order to find out whether the valve is bending or not bending, you will need to remove the timing belt. Further, the piston in the first cylinder is set to the TDC position, after which the camshaft of the gas distribution mechanism rotates 720 degrees. If in the process of turning the camshaft no stop is observed, then it is necessary to make a similar check by alternately raising the pistons in all other cylinders of the internal combustion engine to TDC. If the camshaft does not rest anywhere, then there is a high probability that the valve on this engine does not bend when the belt breaks.

With regard to various technical information, which is given in the tables, as well as referring to the experience of auto mechanics and ordinary drivers, the summary data allows us to note:

often the valve does not bend on simple 8-valve motors;
usually valves bend on 16-valve and 20-valve engines;
valve oppression on almost all diesel engines;
bending of the valves occurs on most engines in the event of an open timing chain, that is, on engines with a timing chain drive;
valves usually bend on engines of small cars with a working volume of 1.1 to 1.4 liters;

The main reasons

Motor device

Car owners of Lada Priora 21126 are interested in knowing the reasons why the valve bends on their car. Auto mechanics claim that on all modern models of this car, as a result of a break in the timing belt, the valve engine bends. The first engines for the front-wheel drive VAZ 2110, in contrast to similar units for the rear-wheel drive, had a volume of 1.5 liters. A little later, similar designs with a volume of 1.6 liters appeared. with 8 valves and one camshaft. Some car enthusiasts do not know if the valve bends on such engines. This process does not occur because the first elements do not meet with the pistons at the dead center. After evolution, new 16-valve units with two camshafts appeared. This allowed an increase in power from 76 hp. up to 92 hp, while the volume of the engine has not changed.

Experts say that such units are also unreliable, since when the timing belt breaks, valves and pistons meet even at the dead center, as a result, the engine bends the second elements on the Priora. Such repairs are expensive. In addition to replacing the valve, sometimes the pistons have to be replaced.

The designers of AvtoVAZ, having modified the 16-valve engine, first installed it on the new VAZ 2112. The engine received the abbreviation 124. The distinctive features of the new unit from the previous analogues are the presence of an updated piston group. They received "grooves" or the so-called "recesses", with the help of which a reliable protection against breakage of the timing belt is created. VAZ 2112 with this engine is considered a reliable and powerful vehicle.

Features of notched pistons

The 10th family of cars was discontinued due to the presence of many technical flaws. The updated family went through major changes that affected environmental issues and increased engine power. It should be noted that all 16-valve engines are currently installed not only on Priora, but also on other VAZ models, including Kalina and Granta. However, the engine bends the valve on every such vehicle.

The exception to the fact that when the timing belt breaks, these parts will not meet with the pistons, are the first eight-valve motors. Modern production of domestic cars does not provide for the use of these units. New eight-valve counterparts with increased power also bend the valve.

Since 2011, Priora had 8 valve motors marking 21114, which did not bend the valve. In recent years, the valve bends on all manufactured Ladakh Priora, since they have engines with 8 valves marking 21116.

Cautions and Consequences

Valve bending on the Priora is mainly due to the meeting of the piston with the first parts. If the timing belt breaks, expensive repairs to the car owner cannot be avoided. In such a situation, auto mechanics recommend:

regularly check the condition of the belt,
determine the presence of chips and cracks on the belt,
check if there are threads on the belt.

Piston system

In this case, you will also need to buy a new, lighter piston group. From an authorized dealer, it will cost no more than $ 2-5. Some auto mechanics recommend buying a car of another brand, the price of which practically does not differ from that of the Priora. It can be KIA RIO or Chevrolet Aveo. This problem can be solved with an optimized cooling system for the block and cylinder head.

Frequent breakage of the timing belt is associated with the use of low-quality car parts, including a bypass roller. To prevent such a breakdown, Priora car owners install on their cars a lower gear on a calender, a belt and rollers from a VAZ-2112. This does not change the pump and gears on the camshaft. Washers 5 mm thick are placed under the rollers. The presence of a large number of manufacturers of these parts allows you to choose high-quality and reliable products for cars.

Some innovations

Upgraded 16-valve engine

The recently released sedans and hatchbacks of the Priora family are equipped with an upgraded engine as standard - a 90-horsepower engine with 8 valves and lightweight connecting rod and piston groups. This power unit was developed in the scientific and technical center of AvtoVAZ. To master it, the manufacturer needed to modernize the lines for the production of main parts and the assembly of motors. Metallurgical production has undergone modernization of the cylinder block casting line.

To reduce the overall weight by 39% compared to the basic version, it was necessary to optimize the cooling system for the head and cylinder block. The engine received a new camshaft drive, including an automatic tensioner, piston cooling nozzles, a metal cylinder head gasket. Reduction of mechanical losses made it possible to increase the motor power from 59.5 kW to 64 kW, that is, up to 90 hp. At the same time, the maximum torque increased from 120 Nm to 140 Nm. This has resulted in reduced vibration and noise levels. The specific fuel consumption also decreased, which led to an increase in the engine resource up to 200 thousand km. The environmental friendliness of the motor has also increased. Carbon dioxide emissions decreased from 175 g / km to 165 g / km.

AvtoVAZ has produced over 700 cars with new engines. The recommended retail price for the Lada Priora in the "Standard" configuration of the sedan type is 8 thousand USD. e., and the hatchback - 8,500 thousand. e. The domestic manufacturer plans to soon apply new engines to Lada Granta and Lada Kalina.

Details Category: News Published on 27.07.2018

AVTOVAZ engines will receive a new piston engine, which will allow to avoid bending of the valves when the timing belt breaks.

As you know, one of the disadvantages of modern engines is the bending of the valves when the timing belt breaks. It is quite difficult to predict the resource of the belt, since it can break off not only due to wear, but also with a jammed pump or tension roller.

When a timing belt breaks, a modern engine usually bends the valves on the pistons. This leads to costly repairs.

AVTOVAZ decided to eliminate this problem, CARscope.ru reports. The plant's supplier, Federal Mogul, has mastered the production of pistons with special notches.

Thanks to this shape, both the pistons and the valves will remain intact, even if the timing belt breaks.

The new piston group is designed for a wide range of engines. This is an 8-valve VAZ-11186 with a capacity of 87 liters. sec., as well as 16-valve engines VAZ-21126 (98 hp) and VAZ-21127 (106 hp), which are installed on the Kalina and Grant family of cars.

The 106-horsepower VAZ-21129 engine, intended for the Vesta and XRAY models, should also receive a version with new pistons soon. But the new VAZ-21179 unit with a volume of 1.8 liters and a capacity of 122 liters. with. until a new piston is received.

One of the scary topics in the conversations of motorists is why the valves bend, on which cars this breakdown is possible, and how to prevent it. Today we will tell you in detail about the reasons why the engine valve fails and the preventive measures for this malfunction.

What are the valves in the motor responsible for?

First, a little theory. Surely every car enthusiast knows how many cylinders there are in the engine of his car, but how many valves it contains - not everyone will give an answer to this question. In most modern engines, there are from eight to sixteen valves (two or four per cylinder), there are power plants (eight or twelve-cylinder), in which the number of valves is from 24 to 32.

The valve is an important part of the gas distribution mechanism (timing) of the engine of the machine, which is located in the cylinder head, is responsible for the timely supply of air to the cylinder and the displacement of exhaust gas from it.

Moreover, the same valve cannot perform these functions, and therefore each cylinder is equipped with two types of valves - intake valves, which supply air to the combustion chamber, and exhaust valves, which squeeze out the combustion products of the air-fuel mixture from this chamber.

There are engines in which there are two exhaust and intake valves per cylinder, and there are those where there are more intake valves than exhaust valves (three and five-valve cylinders). In the structure of the valve, two parts are distinguished: a plate and a stem. It is the valve stem that gets hit when one of the elements of the gas distribution mechanism fails.

The valves are brought into operation by the camshaft, which, rotating around its axis in the cylinder head, raises some and lowers other valves into the cylinders - these are the so-called gas distribution phases. In turn, the camshaft drives the crankshaft - both of these timing elements are interconnected by a drive, which can be gear, belt or chain. A gear train rotates the camshaft in the cylinder block, and a belt or chain drive rotates in the cylinder head.

Currently, the most widespread are engines, in the gas distribution mechanism of which they are used. The belt drive is simpler in design, but less reliable than the chain drive. The chain type of drive, in turn, is more complicated - its mechanism includes tension rollers and dampers. It is no coincidence that we paid so much attention to the details of the gas distribution mechanism - understanding the principle of its operation will help us in the future to determine the reasons why the valve bends.

Why valves bend

Both a belt-driven gas distribution mechanism and a chain-driven timing mechanism may come a moment when a belt or chain drive fails. A break in the timing belt or stretching of the timing chain links that are not able to catch on the teeth of the camshaft gears (slipping) leads to the fact that the camshaft stops abruptly, and the crankshaft continues to move.

At this moment, the valves are recessed into the cylinder, and the piston rises towards them. The lifting force of the piston is much greater than that of descending valves, so the piston hits the valve disc, and the rod, unable to withstand this impact, bends or even breaks. There is a complete stop of the engine, which is not recommended to start again, so as not to provoke more serious damage - failure of the pistons, which is fraught with expensive repairs to the cylinder head.

How to tell if the valves are bent

It is impossible to establish by eye that when the belt breaks or the timing chain slips, the valve is bent. To do this, you need to carry out two simple operations.

To begin with, we will install a new timing belt on the rollers according to the marks and slowly turn the crankshaft. Two to five revolutions are enough to determine that the valves are bent: if the rotation is free, then the valve stems are intact, if it is difficult, the valves are bent.

It so happens that the crankshaft scrolls, but the valves are still bent. How, in this case, to determine the breakdown? It is necessary to measure, having previously unscrewed the spark plugs. If there is no compression in the cylinder, the valves are bent.

How to prevent valve breakage

Let's analyze the reasons why the belt could break in order to understand how to prevent such a breakdown.

Cause 1. The timing belt has expired. Like any other consumable, the timing belt has its own service life. The car manufacturer in the operating manual indicates the timing of the timing belt replacement - for most engines, it occurs with a mileage of 100-120 thousand kilometers. It is certainly possible to hope that up to this point the belt will serve faithfully, of course, but for greater fidelity, we recommend that at each scheduled maintenance inspect the condition of the belt and, if necessary, replace it. In this case, we will not allow it to break, and, as a result, we will not disentangle the problems with bent valves.

Reason 2. Using a counterfeit timing belt. Some motorists, wanting to save money, buy non-original, cheap timing belts that break at low mileage - 5-7 thousand kilometers. Advice - be responsible for buying a timing belt, it is better to pay more for this consumable than to fork out for expensive cylinder head repairs later.

Reason 3. Breakdown of the timing pump. In the design of the gas distribution mechanism of some engines, the pump comes into contact with the belt, and if this unit fails, it jams, as a result of which the belt rubs against the pump and frays, which leads to its breakage. The pump wears out at the same mileage as the timing belt, so when replacing the belt, we recommend installing a new pump.

Cause 4. Camshaft wear. This breakdown occurs at high engine mileage (from 150 thousand km or more), and therefore does not occur so often. A jammed camshaft can rupture the timing belt. That is why when buying a used car with high mileage, we strongly advise you to take a look at the condition of the camshaft.

Reason 5. Malfunction of the timing drive attachment. The timing belt moves on rollers, which can also wear out, jam, which leads to the belt breaking and the valves being bent.

Although engines with a timing chain drive are considered more reliable, it happens that they also have valve bending. This happens for two reasons: the chain links are stretched or the drive attachments (idler rollers and dampers) fail. The main reason why the timing chain links stretch is the poor quality material from which it is made. Such a misfortune happened to Volkswagen engines in the mid-2000s: the German automaker ordered chains from an unscrupulous contractor, and they began to fail at 20-40 thousand mileage, provoking bending of the valves. To prevent such motors from bending the valve, you should periodically diagnose the timing chain and attachments and, if necessary, change them to new ones.

In addition to these methods, it is possible to prevent bending of the valves by making special recesses on the piston heads, which will correspond in size to the valve stems. If a belt breaks or a chain slips through, then when the camshaft stops, the valve rods will not bite into the piston heads, but will enter the grooves and stop there. True, this method also has its drawbacks: an engine with such "tuned" pistons loses up to seven percent of its power. Are you ready to derate the motor of your "iron horse" for the sake of the safety of the valves in case of failure of the timing drive?

As I wrote about the engines "PRIORA", I was asked - "", read it very informative. In this article, I promised to talk about the very principle of why this happens on some engines, but not on others. In general, about the breakdown process itself, today I will try to sort everything out on the shelves, just for you "beginners". I will not delay, let's go ...

So the valve is part G azorasp R a separate m car mechanism (timing). It should be noted that the part is quite important, without them there would be no exhaust gases release, and compression in the cylinders would not be created during fuel injection and ignition. In modern engines, their number varies from 8 to 32. But in most, variants with are used, they are the most common of all.

Principle of operation

"Makes" them work to open and close the camshaft, which is located on top, in the head of the block.

It spins up and, thanks to special ovals, presses on the valve - it opens, or releases it - it closes. In turn, the camshaft runs on a belt or chain drive from the crankshaft.

The distribution and the crankshaft must be synchronized so that the opening of the valves and the movement of the piston coincide in a certain sequence - when the piston goes down, the valves open ("sink" into the chamber), when the piston rises up, they close (go up), thus creating pressure in the combustion chamber, then the candles ignite the mixture and the piston goes down under pressure. This cycle is repeated many times. Here is a short video clip of work for understanding.

This is a perfectly working scheme, with proper maintenance (timely replacement) everything will travel many thousands of kilometers.

The reason why the valve bends

I would like to note that it can be both on 8 and 16 valve engines. The reason is simple - it is a broken timing belt or chain. For the sake of fairness, it is worth noting that the "chain" very rarely breaks, it basically stretches out and the "hook" sprockets begin to jump, which may also be the reason.

When a break occurs, the camshaft stops abruptly, but the crankshaft continues to push the pistons. Thus, the valves are lowered and "drowned" into the combustion chamber, the piston also goes up - which should not be the case during normal operation. They meet at the "high point" and the piston, possessing high energy, simply bends or breaks the valve. As you can see, everything is quite commonplace.

Such a breakdown is very expensive - you need to "half" the motor and pull out the bent elements, sometimes even the block head itself suffers (but rarely), so it will also need to be changed. You can also find damage to the pistons (the valve breaks it), but here it is even more serious, it will be necessary to remove the camshaft and pistons with "connecting rods".

Why does the belt tear and how to protect yourself from it

1) The most common reason is simply not following the manufacturer's instructions for replacing the belt. As a rule, if you have a warranty car, then the replacement will be under warranty, but if you service it yourself, then many people forget or save on replacement. It "comes out" sideways.

2) Poor-quality belt, now there are just a lot of fakes, especially for our VAZ. In fact, they don't even walk 5,000 kilometers (they were in a company car several times), so take the best proven options. Or change to a service station with a guarantee.

3) The pump fails. In some car models, it is also in the engagement of the belt and if it fails, then it will simply wedge, it will wipe the belt in a matter of hours.

4) The camshaft itself wears out. It is made of metal and it is clear that after some time it will wear out (it can jam), although a very long time must pass (high mileage).

5) Timing system tension rollers fail. They can fall off, they can get jammed - in any case, the belt will either break or it will fly off - there is only one end, the valve will bend.

The guys are only protected here. Change the belt in time, as well as the tension rollers and other elements of this system, which are assigned to you according to the regulations. Take "consumables" at official or verified store stations, because fakes are sold much less than originals, here you risk every thousand kilometers, in general, a belt is not a spare part that is worth saving on.

Are there options that don't bend?

Of course there is, but now they are very rare. Once again I advise you - there are models of motors that have not been "bent" before. However, unfortunately, there are practically no such people now. Therefore, many are doing - such tuning of power units.

The bottom line is also banal, simple - instead of conventional pistons, they are installed. Then even if a break occurs, the valves will simply fall into these holes and nothing terrible will happen. You will need to install a new belt and synchronize the camshafts and crankshafts.

“Great,” you say. But why, then, such pistons are not put on all models? After all, this is 100% protection.

Again, everything is simple - such pistons eat up part of the engine's power, and decently. There are still debates about "how much." Some say that by about 5 - 7%, and this is excuse me - GREAT! The thing is that such a piston is heavier, and the compression is not as effective. That is why many have rejected this decision. Many - but not all!