Engine valves operate in heavy duty in the area of ​​high pressure and high temperature and therefore are made of sufficiently durable materials. However, it is not uncommon for a valve disc to burn out, usually it is an exhaust group valve operating in particularly harsh conditions.

This is due to the fact that, when released, hot exhaust gases with high speed and pressure pass between the valve disc and the seat, aggressively acting on both parts.

Signs:

Burning of the edge of the valve disc can also be caused by wear of the valve stems and the hole in the guide bushings. This leads to the fact that the valve has some play in the guide and therefore does not fully seat in the seat.

According to the back side of the cam camshaft it is possible with a high degree of probability to conclude that there was a small valve clearance or was completely absent.

It is defined in this way. When there is the necessary clearance between the rocker, rocker or pusher (depending on the engine design), then the back of the camshaft cam does not touch the mating part. Since there is no direct contact, the back of the fist has a darkish tint, while the working part is always shiny, as it constantly works on direct contact.

When there is little or no clearance, the back of the camshaft cam also works in contact with the rocker and also has a shiny appearance. This will confirm the likelihood that the valve burned out due to clamping the valve clearances during adjustment, or decreased during operation, when the condition of the valve clearances was not checked for a long time.

When the valve disc is fully attached to the seat, it gives off part of its temperature to the seat, while partially cooling. When the valve cannot sit completely in the seat, it practically does not cool, which ultimately leads to its overheating and burnout of the plate edge.

Valve burnout and valve seat wear are especially pronounced in engines operating on. This is due to the fact that when using gas, the combustion temperature rises by 60-80 degrees, relative to the gasoline mixture.

So when working on gasoline, the valve plates heat up to a temperature of about 900 degrees, and the seats up to 300-350 degrees. In itself, such an increase in temperature as a whole is not dangerous for the engine, unless adjustment is made to lean the gas mixture. When working on the combustion temperature rises by 200-250 degrees, which will inevitably lead to the combustion of exhaust valve plates and seats.

In addition to the mechanical causes of valve burning, the use of gasoline, the octane value of which is lower than recommended by the manufacturer, should also be noted. specific brand car. This is due to the fact that the lower the octane number of gasoline, the higher its burning rate and the higher the likelihood of detonation during engine operation.

So, in the normal state of the engine, the flame propagation front of the mixture spreads from 10-20 m / s, and when using gasoline with low octane rating the speed of the mixture begins to burn already at 1500-2500 m / s, which is almost 100 times higher than during normal combustion.

As a result, the temperature of engine parts increases many times, which leads to burnout of valves, seats, pistons. Therefore, you should not test the strength of your engine by saving on a cheaper grade of gasoline with a low octane rating.

The problem with burning valves can also be caused by the constant operation of the car at its limit. It's still not sport car with a specially prepared motor, and ordinary car With serial engine, for city and country driving.

Examination

The engine can triple for several reasons, these are:

Faulty high-voltage, candle tip;

Broken head gasket;

Burnt valve.

For check idle cylinder you need to remove the candle tips from the candles one by one. With a working cylinder, the operation of the engine will immediately change, when removed from faulty cylinder engine operation will remain unchanged.

What to do?

A burnt valve must be replaced under certain conditions. So, if work has already been done to repair the head of the block, namely, replacement of guides, valves, or grinding of existing valves, then it must be taken into account that the seats have already been squandered. That is, the valve disc is deeply recessed into the seat.

For this reason, the end of the valve stem fits the camshaft cam above the permissible limit, which makes it impossible to adjust it (there is no gap). IN similar cases replacement of valve seats is required, or removal of the end part of the valve stem to compensate for its deep seating in the seat.

If these works are not possible for any reason, then the block head is replaced.

Finally

In order not to get into situations with valve burnout, we recommend periodically checking their thermal gaps, additionally with a compression check, which can promptly indicate a malfunction in the valves by reducing the pressure in one or more cylinders.

Indirectly, the fact that the head of the block needs to be repaired will be prompted by the fact that recently installed valves quickly fail. This is due to the fact that the guides or valve stems are worn out. Due to backlash, the rod constantly presses on one edge of the stuffing box, quickly disabling it. At the same time, the valves can no longer fully sit in the saddle and valve burnout is possible.

Engine valve system internal combustion very complex and precise. To solve a problem in the valve system, it is initially necessary to diagnose its cause. Simply replacing a damaged valve won't do much if the cause is misalignment of the valve guide and valve seat. By replacing the valve that burned out, you will not solve the situation if its burnout was due to a “hot spot” on the cylinder head. As long as the hot spot is present, the valves will continue to burn out.

That's why, important point will analyze the causes of failure before attempting repairs. A valve that has burned out or broken, worn guides, or other problems with valve system often represent the end result of a whole chain of events. One problem gives rise to another, which, in end result will cause valve failure.

How to identify a burnt valve?

There are several ways to check the valve for burnout. The most proven and simplest is the search for a non-working cylinder among all. To do this, you need to start the power unit. During his work on Idling you need to remove the caps from the candles. If after that the engine changes speed, then such a power unit is faulty. And if, after removing the cap from the candle, you see that the engine is working as before, then the malfunctions have touched the cylinder.

When the engine starts to triple, you should unscrew the candles and swap them, or replace one of them. When you have swapped the spark plugs, immediately start the engine. If after that it starts up and works normally, then the candle turned out to be working, and another cylinder stopped working.

In the event that such a replacement turned out to be ineffective, then insert the candle back into the cap and put it on the motor and drive it: if a spark appears, then everything is in order, and if there is no spark, then something is wrong with the slider, distributor or cam. The very first sign of valve burnout is smoke coming from the breather, which means that the candle was left without oil. If the piston breaks, then it will fall out of the breather gray smoke and the candle will be covered with oil.

Another valve burnout is checked in one old way: for this, measure the cylinder compression, this is done using a compression meter. Then pour oil into the cylinder with a syringe and then also check the compression. If after these manipulations the compression will not rise, then the valve has burned out. If the compression rises, then a breakdown has occurred in the piston. Many motorists do not want to change a burnt valve, but this adversely affects engine power and fuel consumption.

Causes of valve burnout

There are many reasons for valve failure. It is less common to talk about already defective factory valves, but this is the second of the main causes of failure. The main reason is mechanical and thermal overloads.

One of the leading manufacturers motor valves cited statistics that every fifth released valve breaks due to factory defects. The results of this study were published ten years ago. The control system has improved significantly since that time, although the materials and production processes have not changed. But still, even ultra-modern quality control systems cannot guarantee that the valve you have just purchased is free from any defects.

The defect may be a metallurgical discontinuity included in the alloy that weakens the valve; forging defects leading to the appearance of microcracks; pores and heat treatment errors that give incorrect valve dimensions; poor adhesion of the chrome coating of the valve surface. Therefore, buying new valve, do the following:

- check that the dimensions of the valve comply with the nominal standards, and that the valve is free from obvious defects;

Purchase valves only from reliable and proven manufacturers.

All valves wear out over time. But there are those that fail much earlier than expected, and there are two reasons for this - burnout and breaking. Exhaust valves often burn out due to the fact that their heating reaches significantly higher values ​​than inlet valves. The intake valves are cooled by the incoming air fuel mixture.

The operating temperature of such valves is approximately 400°C. Exhaust valves do not have such a cooling system and, in addition, they still warm up from the flow exhaust gases. During operation, these valves heat up to 650°C, which means they are more vulnerable to burnout and destruction. The high-temperature working environment requires proper characteristics from the alloy that makes up the valve. Exhaust valves are usually made from of stainless steel as a whole, and only their heads. In powerful gasoline and diesel engines working temperature even higher, so the exhaust valve is coated with a stellite coating in the form of an alloy based on cobalt, which prevents its rapid wear.

Heat removal from the intake and exhaust valves is carried out through the directional valve and its seat. Three-quarters of the heat is removed through the valve seat, so it needs good contact with saddle. The rest of the heat is dissipated through the valve stem and then expelled to the outside through the valve guide. If the valve is not regularly cooled, then it overheats and burns out further.

Everything that interferes proper cooling valve or creates excessive overheating, causing the valve to burn out. The formation of deposits on the valve and its seat prevents it from cooling properly and leads to inevitable overheating. It also contributes to bad contact between valve and seat if it is very narrow and not concentric or elliptical.

Too weak a spring or a decrease in valve clearance impairs the mutual contact between the seat and the valve, which again leads to overheating. This is also facilitated by a worn seat or guide, which prevent heat from being removed to the power unit.

When installing the valve, pay attention to its height. Lapped valves located in the cylinder head much deeper than necessary. This leads to higher protruding rods, the geometry of the rocker is broken, and when heated power unit valve clearance disappears. If the required geometry is not restored after grinding the ends of the rods, the saddles must be replaced. Another option is to install a valve with heads slightly bigger size which compensate for the ground seat.

Reduced valve clearance is common cause valve burnout. If the valve seat is worn, it will go deep into the cylinder head and reduce the clearance. As a result, the gap is completely or partially blocked, and the valve does not adhere well to the seat, gets very hot and subsequently burns out. This happens mainly on older engines that do not have hard seats and are installed on heavy trucks, marine, agricultural and industrial machines. The way out of this situation is to install more rigid valve seats with stellite coating.

Valves can also burn out due to problems with cooling system in the power unit itself if its operating temperature becomes extremely high. Lack of coolant, problems with the thermostat, hydraulic pump, clogged, broken fan or fan switch - all this leads to overheating of the power unit. This, in turn, leads to an increase in the valve stems, a decrease in the gap between the guide and the stem, which leads to the stop of the valve in the guides, and it can jam. If the valve is stuck in the open position, the piston will hit the valve, resulting in the destruction of the piston, valve and other parts.

Overheating of the valves also occurs from strong elevated temperature combustion. Factors such as pre- or late ignition, lean fuel mixture, detonation can play a fundamental role here. Similar causes for valve overheating are exhaust obstruction caused by a clogged catalytic converter or pipe damage.

Consequences of valve burnout

If you do not replace a burned-out valve for a long time, but continue to drive, then the first negative consequence will be big fuel consumption due to the fact that the motor is not able to deliver its normal power, and also the valve seat may burn out too much, as a result of which the head will have to be changed. In rare cases, a piece can break off from the valve and get into the cylinder. If this element is too large, then it will be able to pierce the head and piston. IN special occasions the cylinder may also be pierced, which completely disables the power unit.

If you fill your car with gas, then necessary procedure there will be periodic adjustment of the valves every ten thousand kilometers. Gas burns the valves too much, especially in cases where the gas supply is set poorly. For cars that drive gas fuel exhaust valves are often slightly tight. And as soon as you start adjusting the valve, it will jam and burn out. Cars that “eat” gasoline are less prone to valve burnout.

Intentionally do not lean the gas supply in order to save money. Due to a lean gas mixture, the engine loses power significantly, and gas overruns occur more significantly, since you have to squeeze the accelerator pedal more, plus the valves and their seats gradually burn out. When correct setting gas mixture, the power of the power unit grows so much that the difference between driving on gasoline or gas is smoothed out. But don't forget about frequent adjustment valves when driving on gas. Often, motorists decide to adjust the valves only when noise appears, but this is only suitable for those who drive on gasoline. In the case of gas, you should not wait for the appearance of valve noise. The valve will close and burn out even without such obvious signs.

How to fix burnt valve?

When starting this event, be aware that the first step is to remove the head from the power unit. Such a procedure is performed precisely in cases with a burnt-out valve, when it does not hold at all, and the engine starts to triple. Valves of any format are the same, there are differences in size, placement in the head. Lapping is the same everywhere.

You will first need to purchase lapping powder. Dilute its dry composition engine oil, you can the one that you fill in the engine. Pour the powder into a previously prepared container, add oils until a porridge-like mass of medium density is obtained. Be sure to prepare a new one, which you will put under your head, as well as valve seals. Exhaust valves often burn out. There are many reasons - the valve is clamped, a lean mixture was present (when the unit operates on gas), the guide bushings are significantly worn out, the valve stem is worn out.

The carburetor does not need to be removed, as well as the manifold from the head. First, dry out the valve. Lay the head on a flat surface, preferably on a table or wooden shield. Place under the valve rubber mat. You will need a tube with an inner diameter of over 13 mm. Place a tube on the valve so that the croutons are inside. Then strike with a hammer. In this case, the valve is dried out, and the crackers remain in the tube. Now the valve can be pulled out.

Mount new element, gently shaking it. Runout up to a millimeter is considered normal - the guide sleeve can be left. Then try to replace the guide, here you will need a special mandrel. If you decide to knock out a part, act from the inside, in the direction of the camshaft. Here you will need a heavy hammer, semi-sledgehammer. The blow must be confident and heavy. If you use a light tool, the sleeve will crumble.

Try to hammer this valve bushing into the head. The sleeve should easily enter the valve - if it hits the head, the element is compressed. First, put on the retaining ring removed from the old bushing, lubricate the assembly with oil. Hammer the bushing into the hole of the valve head up to the retaining ring. Be careful as the structure is fragile. Do not strike the valve packing area. You can put on the tube, put it on the sleeve, protecting the parts. Place a piece of tin, a piece of wood, on the edge of the bushings, substitute the bolt and carefully hammer it into the head. Having deformed the edge of the sleeve hole, align it using a drill and a needle file.

How to identify a burnt valve in the engine?

Many motorists are faced with the problem of valve burnout, but they cannot accurately determine without removing the head. I will tell you the easiest way to determine valve burnout.

It all starts with the fact that the engine starts to triple, but this sore can be associated with a bunch of reasons, now let's consider valve burnout.

First you need to determine which cylinder is not working, this can be done in the old and proven way, start the engine and let it work on idling, start pulling off the caps from the candles one by one, if you pulled the cap off the candle and the engine changed its speed (it began to spin more slowly or stalls), then this cylinder is working. If, when pulling off the cap from the candle, the engine both spins and spins or slightly changes its speed, then this cylinder does not work and it is necessary to find out the cause of the failure.

Photo. Burnt Zhiguli valve.

The first reason when the engine is troiting is the failure of the spark plug, unscrew the spark plug and replace it with another one, or it’s better to just swap the spark plugs, put it from the working cylinder to the non-working one and put it from the non-working cylinder to the working one and start the engine. If the engine starts up and works as before, then the candle has nothing to do with it, and if another cylinder stops working (this is also checked by pulling off the caps from the candles) and the non-working one works, then you are lucky, you just need to replace the damaged candle.

If replacing the spark plug didn’t help, check if there is a spark on it, put the spark plug in a cap, put it on the engine and drive the engine with a starter if there is a spark, then everything is fine with the distributor, if not, then the distributor cover, slider or cam is most likely to blame, but this is a topic for another explanation.

So the candles checked there is a spark, which means the ignition is working.

Two reasons remain; valve burnout, or piston breakage (occurrence piston rings, broken piston rings, broken piston baffles).

Now let's figure out what is the reason, valve burnout or piston breakage.

Usually, many minders begin to measure compression in the cylinders, and if bad compression in the cylinder they give the conclusion of the burnout of the valve, THIS IS NOT ALWAYS TRUE !!! The thing is that the compression in the engine can drop both due to a burnt valve and due to broken piston rings, this reason can be determined without measuring the compression in the cylinder.

A sign of valve burnout, the candle is dry without oil deposits, with the breather is coming air or slightly noticeable smoke, smoke density depends on the wear of the piston group.

A sign of a broken piston, a candle in oil, blue smoke comes from the breather. But it happens that the candle is dry, slightly smoked, be guided by the breather, if smoke comes out of the breather, this is a breakdown in the piston of the piston rings, or the occurrence of piston rings.

If oil flies out of the breather and there is no smoke, this is a breakdown in the piston of the partitions between the rings.

Based on these signs, you can determine by 99% why the engine is troiting, from valve burnout, or piston failure.

There is another very old way determining valve burnout. To do this, you need a compression gauge in the cylinder, measure the compression in the cylinder. Then pour a syringe of oil into the cylinder, again measure the compression. If the compression rises, then the piston breaks, if the compression does not increase, then the valve burns out.

Valve burnout on the VAZ

I will show an example of determining valve burnout on a VAZ 2105 with a VAZ 2103 engine.

The photo below shows the engine in which I determine valve burnout using the method described above.

The fourth cylinder does not work on the engine (determined by pulling the caps off the candles).

Please note the photo is divided into two shots. The top picture, the engine is running, the breather pipe is removed, there is no smoke, a sign of a whole piston group. Bottom picture, the breather pipe is lowered, and the pan air filter at the junction of the pipe is plugged with a rag, the owner of the car is an aged peasant. Of course, this is not supposed to be environmentally friendly, but he deliberately removed the breather from the air filter so that the gases that come out of the breather do not smoke the carburetor, and the engine runs only in clean air.

Photo. The engine in which we determine valve burnout

I unscrew the candle from the fourth cylinder, the color of the contacts of the candle says that the candle is working, moreover, the engine is well tuned, since Brown color candles says that the working mixture is normal, not poor, not rich. I didn’t even change the spark plug, everything is clear, valve burnout.

But, the same sign can be in contact ignition, the thing is that the contacts, as the cam wears out, may almost not open, this will also give the engine tripping, but usually at this moment the candle is a little smoked. Also, when working at idle, the engine can pick up and stop troiting at times. Therefore, be sure to check if there is a gap in the cantatas of the distributor. The distributor bearing may also deteriorate, a sign if you shake the contacts, they begin to dangle strongly to the sides, change the distributor bearing or buy a new distributor. Therefore, if the engine is trot, first of all, look at how the contacts in the distributor open. Another sign of a very small gap in the contacts, the engine began to start poorly, especially in the morning and troit at different intervals. When the valve burned out, the engine troit in the same rhythm.

Photo. Spark plug from a non-working cylinder, but the spark plug itself is working without signs of malfunction.

Below in the photo is a burned-out valve, it was replaced with a new one, and all the rest just got used. If you change at least one valve, do not be lazy, grind all the others, and replace the valve seals with new ones. Then this head will work for a very long time.

Photo. Burnt valve

Below in the photo is the intake valve, in soot, it is advisable to remove it, since soot will interfere with good filling of the cylinder working mixture. It is shown how to chip off carbon deposits from the valve with pliers or wire cutters.

Many people have a question, change all the valves to new ones, or you can grind the old ones. It is necessary to pay attention to the valve caps, if they are without obvious defects, you can grind them. Also, be sure to pay attention to the valve stem, this place is indicated by an arrow, as the valve stem wears out and can begin to hang out even in a good guide bushing. The method of determining is simple, in the place indicated by the arrow, slide your finger, you will feel the unevenness of the stem (output), the valve must be changed to a new one (you can leave this one too, but the likelihood of excess noise and burnout will increase). There is no wear on the valve that is in the photo, I rubbed it in the place where it stood.

Tip, grind the working valves to the valve seat where they stood.

Photo. Carbon deposits on the intake valve, and how to remove it

Consequences of valve burnout

If the burnt-out valve is not changed for a long time, but is driven, then the first wakes up high flow fuel, since the engine does not give out its normal power, and the worst thing is that the valve seat starts to burn out, the valve seat can burn out very much that you have to change the head, or take the head to a specialized workshop to replace the valve seat. Rarely, but it may be so, a piece of the valve breaks off and falls into the cylinder, if a large piece then khan the piston and hit the head hard, if a small piece, then beat the head and piston. I saw the engine when the valve hat completely flew off and broke the piston, head (this is half the trouble), but it also pierced the cylinder in the block VAZ engine(Khana engine) due to a defective new valve.

Valves burn out different reasons, the valve was stuck, a very lean fuel mixture (especially if the engine is running on gas), extensive wear on the valve guide (the valve is loose in the guide), or wear on the valve stem itself (abrasion of the valve stem).

If you drive on gas, then it is advisable to adjust the valves every 10 thousand kilometers, the gas burns the valves very much, especially if the gas supply is very poorly configured. I noticed that when adjusting the valves, those cars that run on gas are almost always the exhaust valves slightly tightened (not yet clamped, but the probe no longer passes), and as soon as the valve adjustment is started, the valve will definitely close and burn out. And those cars that run on gasoline are less prone to valve burnout.

Do not try to deplete the gas supply trying to save money, because lean mixture the engine loses power and vice versa, there is an excessive consumption of gas, since you have to put more pressure on the gas pedal, plus the valves and valve seats burn out. When the gas is set correctly, the engine power increases and there is no difference when driving on gasoline or gas. But do not forget to adjust the valves more often when driving on gas. Usually they come to adjust the valves when valve noise appears, but this is suitable for those who drive on gasoline, when driving on gas, do not wait for valve noise to appear, most likely it will not appear, and the valve will close and burn out.

Signs of valve burnout. Video

Gorobinsky S.V.

Valves ensure the implementation of working processes in the cylinder. The intake valves are responsible for supplying a portion of the fuel-air mixture, and the exhaust valves are responsible for the release of combustion products. Burnout of one valve adversely affects the operation of the entire cylinder.

What does a burnt valve look like?

Signs of a burnt-out valve include engine tripping, smoke from the breather (a breather is a valve for crankcase ventilation and excess pressure release), and when long work engine with a burnt valve - an increase in fuel consumption. Let us explain the popular concept of "motor troit". This means a malfunction of one cylinder, which manifests itself in the loss of power and throttle response, the appearance of vibration and shots in the exhaust pipe.
But these signs of a burnt valve are ambiguous.

The engine may also thrive due to idle candles or weak spark.

Smoke from the breather can also be caused by damage to the piston. But there is hallmark- the color of the smoke should be gray, and the candle is covered with oil, which is associated with a broken piston. In case of burnout, the candle remains dry.
Note that a burnt valve in carbureted engine and in the injector gives the same symptoms, tk. the difference is only in the fuel injection system.

How to understand that the valve is burned out?

If you checked the candles, but the engine is still troit, then you should proceed to the procedure for searching for an idle cylinder. She is uncomplicated. After starting the engine at idle, remove the caps from the candles one by one. If, when the cap was removed, the engine changed the mode of operation, this means that the cylinder is working. If the changes have been insignificant, then the cause should be sought in this cylinder.

Removing wires from spark plugs

Next, you need to check the compression of the suspicious cylinder. We measure the compression level with a compression gauge, and then repeat the measurement by pouring an oil syringe into the cylinder. If the second value is higher than the first, then the problem is with the piston. If the values ​​match, the valve burns out.

Why do valves burn out?

The valves operate at constant high temperatures ah (400-600°С) and significant mechanical loads. Inlet valve be in more gentle thermal conditions, tk. cooled by the incoming fuel-air mixture. exhaust valves on the contrary, they heat up even more due to the exhaust gases.

Exhaust valves are more likely to burn out.

For correct operation valves, a clear fit of the valve to its seat must be ensured and the conditions for their cooling (opening-closing level) must be observed. The appearance of soot on both the valve itself and on the seat violates both requirements and leads to valve damage. Carbon deposits can form due to under-adjustment, wear, factory defects, problems with the cooling system, elevated combustion temperatures, etc.
A factory defect is not uncommon. The part is complex, it works under conditions of constant loads, so even a slight inhomogeneity of the metal can lead to the destruction of the entire part.

To protect yourself from marriage, buy only from trusted manufacturers!

Wear is an insurmountable obstacle for all working parts. Therefore, do not neglect valve checks after a certain mileage! Bad adjustment valves is the creation of insufficient clearances between the valve and the seat, which is often referred to as pinched valves.

How will the engine work and what will happen if the valves are clamped?

How to understand that the valve is stuck

If, after starting, the engine runs normally, but the thrust drops during long operation, this is a symptom of stuck valves. Another sign of stuck valves may be shots in the muffler when the gas is released. Because the combustion chamber is not completely closed, the compression is reduced and the work process is disturbed. It is better to exceed the allowable gap when adjusting than to make it smaller.

A burnt valve must be repaired as soon as possible!

Clogged valves result in overheating, increased consumption fuel and, as a result, burnout. It is undesirable to operate the engine with a burnt valve, this leads to burnout of the valve seat. What will result in the car owner replacing the entire head.

What to do if the valve burns out?

In the case of burnt valves, the repair consists not only in replacing them, but also in finding out the cause of the burnout. Therefore, the ignition and cooling systems should be checked.

If you have replaced and lapped one valve, take the time to lap the rest.

You can replace the valve not only at the service station, but also in the garage if you are familiar with the basics of repair.

Thus, the valve important detail motor, therefore, in order to protect yourself from repairs, it is better to carry out maintenance work during.

The valves are part of the gas distribution mechanism and are responsible for opening and closing the intake and exhaust ports through which the fuel mixture enters the cylinders and exhaust gases are removed. Since the valves are constantly working under critical thermal loads, it happens that they burn out. If experienced motorists are well aware of the signs of a burned-out valve, then they are most often unknown to beginners, as well as why these parts become unusable, what it threatens and how to repair after burnout. Let's try to fill these gaps in knowledge.

Since the valves of internal combustion engines are made of high-strength and high-temperature-resistant metal alloys, they, of course, cannot “burn” in the classical sense of the word. valve burnout is technical term, which means that a crack has formed on its edge or penetration has appeared. Due to such defects, the tightness of the fit of its plate to the seat is lost, which inevitably leads to problems in the functioning of the engine and can cause serious damage to it.

Why do valves burn out?

What does a burnt valve look like?

Specialists highlight whole line the reasons why the valves of internal combustion engines burn out. The most common and common of these are the following:

• Factory marriage of the parts themselves;
• Incorrect adjustment;
• Malfunctions of the cooling system of power units;
• Malfunctions and wear of other parts of the gas distribution system;
• Prolonged operation of the engine on a lean fuel mixture.

Not so long ago, one of the companies specializing in the production of automotive components, cited statistics showing that about 20% of failed valves break down due to factory defects. Now many companies are engaged in the production of these parts, and among them there are those that do not fully comply with the technology of their manufacture. Valves from these manufacturers most often burn out. As for the defects due to which they fail, they are the inhomogeneity of the metal; flaws that appear during forging and improper heat treatment; microcracks; poor adhesion of the valve surface coating.

A fairly common cause of valve burnout is incorrect adjustment of their thermal gaps. It leads to overheating of parts with all the ensuing consequences. It should be noted that for this reason, the valves of both those engines in which they are regulated manually, and those in which this process is carried out automatically, burn out. In the second case, for the adjustment thermal gap hydraulic lifters respond, and if for some reason they fail, the valves begin to overheat.

Their temperature can also rise excessively when the engine is not cooled well. This may be due to problems with the pump, thermostat, clogged radiator, or a simple lack of coolant.

It often happens that in the process long-term operation engine valve guides wear out. This, as well as such a defect as weakening the elasticity of the pressure spring, often leads to incorrect positioning of the part and, as a result, its overheating and burnout. In addition, valves often burn out even when engines run lean for a long time.

Signs of burnt valves

The surest sign that a valve (or several valves at once) has burned out in the engine is that it begins to “troit”. In principle, this also happens when malfunctions occur in the car’s ignition system, however, if after checking it turns out that everything is in order with it, then it makes sense to check the valves.

Another symptom that signals this malfunction is the loss of power and throttle response of the machine. There can be many reasons for this car behavior, but valve burnout is one of the most common of them. Finally, another sign is the appearance of periodic pops both in the suction manifold and in exhaust system(muffler).

If it turns out that the valves have really warmed up, then repair should not be postponed. The fact is that operating an engine with burnt valves is fraught with even more serious problems.

Possible consequences of valve burnout

As practice shows, the most harmless of all the consequences that the operation of a car with burnt valves threatens is an increase in fuel consumption. The fact is that the power unit begins to work unstably, as a rule, more fuel mixture enters the combustion chambers of the cylinders than necessary.

It is much more dangerous that when operating an engine whose valves have burned out, fragments may enter its cylinders. Burnt valves lose their strength, are steadily destroyed, and metal particles may well fall (and, most often, fall) directly into piston group and destroy it. This can lead to the need for serious engine repairs, up to complete replacement cylinder heads. If, under such conditions, you continue to operate the power unit, then, in the end, it will have to be completely changed.

Repair after valve burnout

When, during the diagnostic process, it turned out for sure that the valves were burnt out, it is necessary to stop the operation of the engine and start repairing it. First of all, it is necessary to eliminate the causes of the malfunction, because if this is not done, then it will certainly occur again.

If it is established that the cause of the burnout of the valves was their incorrect adjustment, then you need to replace them with new ones and adjust them correctly. IN modern cars to eliminate such a problem, it is often necessary to also change the hydraulic lifters.

When the guide bushings are worn and the springs are weakened, they must also be changed along with the valves. To replace them, you should select only parts that are made by well-known and reliable manufacturers in order to be completely sure of their high quality.

In cases where the cause of valve burnout was a malfunction of the engine cooling system, then it is necessary to repair it first of all, and only then proceed to replace the valves. Finally, in any case, you should stop using low-quality fuel and change the operating modes of the power unit so that it does not work on a lean fuel mixture.

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