Signs of burnt out valves. Low compression in the cylinder. Replacement of valves
Modern engines are equipped with a complex systemvalves. In addition, the design is not simple, it is also highly accurate, but this in no way protects the valve from damage. Unfortunately, burnt valves are quite a common problem for both petrol and diesel power units.Symptoms of burned valves can not be observedonly 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, this problem occurs because the thermal clearance has not been adjusted in time. On motors where the adjustment of the gaps is automatic, the hydraulic compensators may break down - as a result, the valve simply burns out.
There are several most popular reasons, the totalwhich one - the valve went burnt. 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.
Working temperature of the exhaust elements is about400 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 why they burn outvalve. 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 - metallurgicalthe inhomogeneities that enter 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 immediatelyto be destroyed. 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, which is actually a failure of not only the piston group and cylinder head parts, but also the cylinder block.
Do not exploit the engine in whichSymptoms of a burnt out valve are observed. This is fraught with high expenses for repairs, and in the worst case - to replace the entire engine. 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 burned-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 burned valves -this is the engine's throttling. This effect is very noticeable, and it can be observed in any mode 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 certaindifficulties. 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 enter 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 burned valvescan be observed on older models of cars, engine parts 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 burned out, the symptomsand the problems will hide in the ignition system. Very often auto mechanics, whose work experience is still small, first of all start diagnostics and repair exactly the ignition.In the process of such repairs, the lid is replacedtrambler, high-voltage wires, candles are replaced. Also set the angle of ignition - the result, of course, no and will not. The engine as it worked, and it 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
At the first stage, it is necessary to determine the cylinder,which 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 working on the idler, the candle caps are removed.
Next, you need to carefully monitor howthe motor works. If the unit is 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, a candle on the foundcylinder and is replaced by a known one. It would also be superfluous to check the high voltage lead to it. Additionally, 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.
The most common and effective methoddetermination of the burned-out valve - compression measurements. 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 any signs of a burnt out valve on the VAZ-2109 or any other car, you will have to diagnose the car in addition.The easiest way to help determineburnout, after measurements - pouring a small amount of oil into 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 inspectionCandles with a problematic combustion chamber. If the candle does not have a characteristic plaque, then this is a clear sign of a 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 / cm3, and for VAZ-2110 - 13 kg / cm3. For most cars, the compression level is 11 to 13 kg / cm3. If the measurements show smaller figures, then you need to diagnose the motor. Probably, the valve has burned in it.
The first signs of a valve burnout are an excuse forspeedy engine diagnostics. If the motor requires 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 begin to appear. You should also know what compression should be in the engine to detect the failure in time and eliminate it without consequences.For those who want to save and operatecar on gas, you should pay maximum attention to the adjustment. On such engines it is recommended to carry out adjustment of thermal clearances every 10 thousand km of run. Engines on gas are at risk, while gasoline burns happen less often.