Signs of burnt out valves. Low compression in the cylinder. Replacement of valves

Modern engines are equipped with a complex valve system. In addition, the design is not simple, it is also highly accurate, but this in no way protects the valve from damage. Unfortunately, burnt-out valves are quite a common problem for both petrol and diesel power units. Signs of burnt-out valves can be observed not only on older engines, but also on relatively fresh ones. It is not possible to operate the engine with a burnt-out valve, and therefore it will be useful for novice motorists to find out where the problem is coming from, what to do in this case, what are the symptoms of this trouble.

Why burn the valves?

In fact, there are a lot of reasons. For those engines where the manufacturer recommended periodic adjustment of the valves, such a problem occurs because the thermal clearances have not been adjusted in time. On motors where the process of adjusting the clearances is automatic, the hydraulic compensators may break down - as a result, the valve simply burns out.

There are several most popular reasons, the outcome of which is one - the valve has gone brown. So, the first reason - the parts are very tightly clamped. Further, the valve guide bushing is in a state of severe wear. It is also often possible to observe the wear of the rod. And one more reason - the work of the engine on a lean mixture, especially the problem of burnout is the owners of cars working on gas. Most exhaust elements are burnt. They are heated to much higher temperatures than the intake ones. The inlet valve is cooled by a mixture of fuel and air during operation.

The working temperatures of the exhaust elements are about 400 degrees. This valve, unlike the intake valve, does not cool down at all, in addition it is additionally heated because of the exhaust gases. Further, these valves are heated to about 650 degrees.

A large percentage of spare parts spoilage is a problem for a motorist

These are not the main reasons, because of what the valves burn out. The leading manufacturer of these parts did a little research, and the statistics turned out not joyful - every fifth detail that is released, broken or burned out due to human factors and marriage. And even modern quality control of products at factories does not guarantee that the part is free of any defects. Another reason - metallurgical heterogeneity, which is included in the alloy. These heterogeneities make the valve weaker than it should be. In addition, there are defects in production, namely forging. This leads to microcracks. Errors in the process of heat treatment lead to the fact that the dimensions of the product vary.

Consequences of burnout

If the valve has burnt out, it can immediately collapse. Shards of it will fall into the combustion chamber. As a result, the engine will be seriously damaged - serious repairs will be required. Thus, the pistons, the cylinder head and the cylinder block are severely damaged. There is still a serious risk that large pieces of the destroyed burned valve will just break through the cylinder block, and this is actually a failure of not only the piston group and cylinder head parts, but also the cylinder block.

It is not necessary to exploit the engine, in which symptoms of a burnt out valve are observed. This is fraught with high costs for repairs, and in the worst case - to replace the entire motor. It is better to notice the problem in a timely manner, and then from the consequences - only the replacement of valves. The consequences of operating a car with a burnt out valve may be different - from a significantly increased fuel consumption to a fully burnt valve seat.

Symptoms of the problem

So, the main signs of the burned-out valves are engine throttling. This effect is very noticeable, and it can be observed in any modes of operation of the power unit. In addition, the motor loses a lot in power. Another reason is the high fuel consumption. In the diagnosis of this breakdown there are certain difficulties. The fact is that if the valve is burnt out, the symptoms are very similar to other malfunctions. In this case, the owner of the car will be sure until the last, that this is another, minor breakdown. These are extra costs and actions.

Function of valves in the engine

The valve in the motor plays an important role. This part allows the fuel-air mixture to flow into the cylinders. In addition, the valves are responsible for the release of exhaust gases after the end of the cycle. The element constantly works in very heavy, even aggressive conditions. They are constantly exposed to high temperatures and gases. Over time, the metal parts are destroyed and burned.

Especially often the signs of burnt-out valves can be observed on old car models, the engine parts of which are made from far from high-quality materials. Most people create these troubles for themselves. Often the motor runs on a low-quality and sometimes not even fuel-specific fuel. As a result, higher combustion temperatures result in damage and destruction of the cylinder head.

Difficulties in diagnosing

There is an opinion that if the valve has gone out, the symptoms and problems will hide in the ignition system. Very often auto mechanics, whose work experience is still small, first of all start diagnostics and repair of ignition. In the process of such repairs, the cap of the trambler is replaced, high-voltage wires, candles are replaced. Also set the angle of ignition - the result, of course, no and will not. The engine worked and will work. The mechanic will search for the problem further, not knowing about the true cause of the problem. Even those locksmiths who guessed that the problem lies in the engine, see signs of burnt-out valves only after removing the cylinder head.

Diagnosis of the burnout of the valve without removing the cylinder head

The first step is to determine the cylinder that does not function. Test methods are similar to the process of diagnosing non-working candles. For the test, the motor is turned on and, when it is operated on the idle, the candle caps are removed.

Next, you need to carefully monitor how the engine works. If the unit affected even more than before the test, or even completely stalled, then this cylinder is all right. However, if the nature of the engine has not changed, this indicates a problem in the cylinder. After that, the candle on the found cylinder is unscrewed and replaced with a known one. It would also be superfluous to check the high voltage lead to it. In addition, check the ignition coil. Further start of the motor will show where the problem has disappeared. If the motor after changing the candle and other parts does not change the nature of the work and continues to touch, there is a high probability that the valve still burned out.

Fault location

The most common and effective method for determining a burned-out valve is measuring the compression. If the results showed a low compression, then this is clearly a sign of burnout. But here it is necessary to take into account a small nuance - with the help of compression measurements it will not be possible to eliminate defects of the CPU. Low compression is not only due to burnout. Various other defects can reduce it - for example, it can be a breakdown of the rings. Therefore, if there are all signs of a burned valve on the VAZ-2109 or on any other car, it will be necessary to diagnose the car in addition. The easiest way to help determine the burn, after measuring - pouring a small amount of oil in the cylinder. Then the compression is measured again. It should grow - this indicates that an oil film was created. This is typical for a worn piston system. If the compression has not changed, then this is definitely a burnout. The way out is by replacing the valves.

Another way to diagnose is visual inspection of the spark plug from the problem chamber of combustion. If there is no characteristic plaque on the candle, then this is a clear sign of burnout of the valves. In addition, air or smoke will escape from the breather.

Compression in the engine

Compression is called pressure, which creates a piston in the cylinder at the time of finding the first at the top dead center.
What kind of compression should be in the engine depends on the type of motor. For example, for VAZ-2109 normal compression is 11 kg / cm ³ , and for VAZ-2110 - 13 kg / cm ³ . For most cars, the compression level is 11 to 13 kg / cm ³ . If the measurements show smaller figures, then you need to diagnose the motor. Probably, the valve has burned through it.

Summarize

The first signs of a burnout of the valve - this is the reason for the speedy diagnosis of the engine. If the motor requires the adjustment of the valves, then these operations should be carried out strictly according to the manufacturer's regulations. Do not wait for the noise to start. Also, you should know which compression should be in the engine to detect the failure in time and eliminate it without consequences. For those who want to save and operate the car on gas, you should pay maximum attention to regulation. On such engines it is recommended to perform adjustment of thermal clearances every 10 thousand km of run. Engines on gas are at risk, while gasoline burns happen less often.