Such a nuisance as a burnt valve is a fairly common occurrence that occurs on both gasoline and diesel engines, and it is not only characteristic of old engines with high mileage. This "sore" can also occur on very fresh engines. Timely detection of valve burnout can significantly reduce the cost of engine repairs and minimize the consequences. It is also important to understand that operating such a motor means seriously exacerbating the problem.
Why does valve burnout occur?
The reasons can be very different, for example, untimely valve adjustment. Due to the violation of the thermal clearances of the valves, carbon deposits appear on the surface of the seats, as well as various derivatives of the increased clearance. In motors equipped with hydraulic lifters, adjustment is not needed, however, failure of one of the hydraulic lifters can lead to a burnt valve.
So, we list the causes of valve burnout:
- Increased wear of the guide bushing or the rod itself;
- Excessive clamping of valves;
- "Poor" mixture (usually found on cars with LPG).
Valve burnout - consequences
As I said, the consequences are different, it all depends on at what stage, or rather, how quickly valve burnout is detected. The most innocuous thing to expect is increased fuel consumption. If the problem is not fixed in time, then you can get burnout of the valve seat, which sometimes simply cannot be restored, so quite often the only way out is complete (cylinder head).
The second danger in the case of a burnt valve is fragments in the engine cylinder. After the valve burns out, it collapses, as a result, pieces of this valve can enter the cylinder, where, when interacting with the piston group, they can disable it. Moreover, fragments leave scratches and defects on the walls of the cylinder head or BC. Prolonged operation of a motor with such a defect can lead to a complete failure of the entire power unit.
How to determine valve burnout?
Engine troit. Most often, valve burnout is accompanied by "triple", that is, when only 3 out of 4 cylinders work, while the sound of the engine and its manner change greatly. Trimming is accompanied by a drop in traction, as well as an increase in fuel consumption. The problem of detecting valve burnout is that there are quite a few reasons why the engine troit, most of them are described.
Checking engine compression and finding a non-working cylinder
Finding a non-working cylinder can be quite simple, the method is old, but very effective. With the engine running, the BB wires are removed in turn, while paying attention to the operation of the motor. If, when removing one or another wire, the operation of the engine has not changed and the motor is still troit, then the reason is in this cylinder. If you removed the wire, and the engine became even worse, and it began to work with even more interruptions, then this cylinder is working.
Next, you need to make sure that the candle is working and it's not about her. Checking a candle is quite simple, I think everyone knows these primitive methods. The easiest way is to take and swap the spark plugs or install a new spark plug and check again if the operation of the motor has changed.
After, in order to exclude the possibility of a faulty BB-wire, it is necessary to check it, how to do it is written.
It also does not hurt to check the coil, how to do it read.
If all of the above assumptions are not justified, there may still be burnout of the valve.
A burnt valve means cylinder depressurization, therefore, a decrease in compression, so it will not be superfluous to check the compression in the cylinders. Read: . After checking the compression, it is recommended to re-check, only using a few "cubes" of oil. A few grams of engine oil is poured into the spark plug well and the compression is rechecked. If, after pouring oil into the cylinder, the compression increases, it can be concluded that the oil film acted as a sealant, as a result of which the increase occurred. This phenomenon is typical for a worn piston group, otherwise, when the compression remains low, valve burnout is quite possible.
Summing up
Valve burnout is an unpleasant phenomenon that can cause irreparable harm to the motor, but if a breakdown is detected at an early stage, problems can be avoided and the repair cost will be minimal. If your car's engine requires regular checking of valve clearance, do not ignore this procedure, otherwise you may experience valve burnout. Regularly monitor the condition and level of engine oil and change it in time.
Only by following these simple rules will you be able to protect yourself and your car from the appearance of such problems as valve burnout in the engine. I have everything, thank you for your attention, I hope you liked the article and share it with your friends using the social buttons. networks below. Bye everyone!
I advise you to watch a video on how to detect valve burnout
Motors. This malfunction occurs both on relatively “fresh” engines, and on power units with impressive mileage. At the initial stage, it is extremely important to accurately determine the nature of the malfunction, since further operation of the engine with valve burnout greatly aggravates the consequences of such a breakdown and leads to costly repairs.
Read in this article
Why valves burn out
Valve burnout occurs for various reasons. For motors that require periodic valve adjustment, valve burnout often occurs due to untimely. On engines with automatic adjustment of the specified gap, the failure of hydraulic lifters also often leads to the fact that the valve burns out.
The main causes of engine valve burnout are:
- valves are tightly clamped;
- worn out ;
- the stem of the valve itself is worn out;
- the engine runs on a lean mixture (especially if equipped);
The consequences of driving with a burnt valve vary, ranging from increased fuel consumption to valve seat burnout. In some cases, a burnt valve seat leads to the need to repair the seat or even completely replace the cylinder head.
A burnt-out valve can collapse at one moment, after which valve fragments fall into the engine cylinder. As a result, serious piston damage, defects or damage can occur. In the latter case, there is a risk that a large piece of a burnt valve will pierce the engine block, which is the actual failure of not only the block head and piston group, but also the cylinder block. In such a situation, prolonged operation of the motor with a burnt valve may lead to the need to replace the entire engine.
Symptoms of a burnt valve
The main sign of valve burnout is noticeable engine tripping in different modes of operation. Also, in the case of a burnt valve, the engine loses power greatly, fuel consumption increases markedly. A certain difficulty in diagnosing burnt valves without disassembling the engine and removing the cylinder head is that the motor can triple for various reasons:
- wear, decline;
- problems with, malfunctions, etc.;
- malfunctions in, malfunction of injector nozzles;
Determination of valve burnout without removing the block head
The first step is to determine the idle cylinder. The test methods are much like diagnosing faulty spark plugs. To check, start the engine, after which, with the engine running at idle, you will need to remove the caps from the spark plugs one by one.
After removing each candle cap, you need to carefully monitor the idle speed and the overall stability of the engine. If the engine starts to triple or stall, then the cylinder from which the cap was removed is working. In the event that after removing the cap, the operation of the engine does not change or the speed changes slightly, then the problem cylinder is detected.
Then you need to unscrew the spark plug on the idle cylinder and replace it with a known good one, and also check the high-voltage armored wire of this cylinder for operability. Also, it will not be superfluous to check the ignition coil, etc. The subsequent start of the engine will show whether the problem lies in the elements of the car's ignition system or further diagnostics are necessary.
If the nature of the engine operation after installing a working spark plug, replacing the high-voltage wire and checking other components of the ignition system does not change (the engine continues to triple), then there is a high probability of more serious breakdowns:
- valve burnout;
- CPG malfunctions;
Valve burnout means that the compression in the cylinder decreases due to a violation of the tightness of the combustion chamber (leaks during the fit of the intake or exhaust valve, destruction of the valve disc and / or valve seat). The wear of the cylinder-piston group and the breakage of the piston also lead to low compression in the problem cylinder. Also, the cylinder may not work due to the occurrence or breakage of the piston rings.
Now it is necessary to localize the malfunction, that is, to accurately determine valve burnout or identify problems with the CPG. The most common way to determine burnt valves is to measure the compression in the cylinders.
Low compression clearly indicates a malfunction, but one caveat should be taken into account. Installing valve burnout and eliminating CPG problems only by the compression indicator will not work. The fact is that the compression in the engine can decrease both as a result of a burned-out valve, and due to broken piston rings, as well as a number of other defects. For this reason, in parallel with measuring compression, additional engine diagnostics should be carried out.
- The easiest way to determine valve burnout after you have measured the compression in the cylinders is to pour a few "cubes" of engine oil through the spark plug well. Then the compression must be measured again. Raising the compression in the cylinder after filling the oil will indicate that an oil film has formed, which plays the role of a "seal". This phenomenon is typical in the case of piston wear. If the compression indicator has not changed, it means that the valve burns out, since the oil in the cylinder in this case will not affect the compression in any way.
- Also, to determine valve burnout, you should inspect the spark plug on the problem cylinder. A clear sign of valve burnout is that the spark plug will be completely dry, that is, it does not have a characteristic oil coating. Smoke or air may also come out of the engine breather. The intensity of the appearance of smoke directly depends on the degree of wear of the CPG.
As for the breakdowns that are associated with the piston, the candle in this case is covered with oil, and bluish smoke can be observed from the breather. Note that the oil on the candle is an indirect sign. Even if the spark plug is dry or covered with a little carbon, but smoke comes out of the breather, then this symptom indicates problems with the piston or piston rings. On new engines with low mileage, it is highly likely that.
We add that the appearance of engine oil that exits through the breather also indicates a malfunction of the partitions between the piston rings. In view of the foregoing, it is possible to determine exactly why the compression in the engine has decreased, to identify problems with the cylinder-piston group, or to determine the burnout of the timing valves.
Summing up
To begin with, the appearance of the first signs of burnout of the valves is the reason for the immediate diagnosis of the motor. If the engine requires periodic valve adjustment, then this procedure must be carried out strictly according to the regulations. You should not expect the moment when noise or valve knock appears.
On vehicles that operate on gas, it is necessary to pay increased attention to the issue of valve adjustment. On such cars, it is desirable to adjust the valves every 10 thousand km. mileage, that is, in parallel with an oil change at a scheduled maintenance. The fact is that burnout of the exhaust valve in gas engines is much more common compared to gasoline.
The desire of the driver to save as much as possible on fuel after installing HBO is often expressed in the fact that the owner asks the tuners to make the car economical. Masters impoverish the gas supply, as a result, the engine noticeably loses power, but there is no significant reduction in gas consumption. The fact is that in order to maintain a dynamic pace of driving, you have to actively press the accelerator. In parallel with this, the lean mixture literally burns out the valves and seats, with all the ensuing consequences. A high-quality setting of HBO implies an almost complete absence of a difference in throttle response when driving on gasoline or gas.
Read also
Valve knocking on a cold engine or after warming up the engine: possible causes of valve knocking. Troubleshooting, useful tips.
Valve burnout is one of the most common car engine problems. Both intake and exhaust valves can burn out. In this case, to one degree or another, part of the working surface of the valve disc is destroyed.
The tightness of the combustion chamber during the compression stroke drops, the compression decreases, the necessary conditions for igniting the fuel mixture are absent, the cylinder stops working normally. As a result, the performance of the car deteriorates, the engine life decreases.
Signs of a burnt valve
- The engine "troit" at idle.
— Flapping exit of exhaust gases from the muffler.
- Increased fuel consumption.
- Deterioration of the dynamics of the car.
The power and throttle response of the engine are greatly reduced.
the working surface of the valve disc is most often subject to destruction (burning) Causes of valve burnout
— Prolonged driving on a lean fuel mixture.
- Long-term operation of the car on late ignition.
— Too small gaps in the valve mechanism.
- Prolonged overheating of the engine.
- The use of low-quality fuel or engine oil.
- Poor quality of spare parts (if the engine was rebuilt).
How to determine if a valve is burnt out or not
— Measurement of compression.
It is necessary to check the compression in the engine cylinders, in the cylinder where it is reduced, the valve may burn out. To finally make sure of this and exclude wear of the piston rings (which also affects the amount of compression), pour 10-15 cubes of engine oil into the cylinder through the candle hole and measure the compression again. The compression readings in the suspicious cylinder have leveled off compared to the rest - worn (lay down, burnt, etc.) piston rings, no 99 percent problem with the valves (in rare cases, cracks in the block or head).
More about measuring compression and analyzing compression gauge readings:.
- Blowing with compressed air.
We set the piston in the cylinder to top dead center, corresponding to the compression stroke. We direct a stream of compressed air from a compressor or pump into the spark plug hole of the cylinder. If the exhaust valve is burnt out, the air will go into the muffler, if the intake valve - into the carburetor.
Notes and additions
- In addition to burnout, similar symptoms are possible if other problems with the valves occur: heavy carbon deposits on the valve plates, shells and cavities on the working surface of the valve plates, too large thermal gaps in the valve drive. All of them lead to a loose fit of the valve disc to the seat in the head and, accordingly, a violation of the normal operation of the cylinder.
As you know, the engine uses a lot of complex systems. One of these is the gas distribution mechanism. Now many are discussing the problems of a broken belt or a loose chain. But few people mention such an element as a valve. It is this part that is responsible for the intake of the combustible mixture and the exhaust gases. One of the characteristic malfunctions is burnout. What are the symptoms of a burnt valve? More on this later in our article.
Why is this happening?
This error occurs for various reasons. Moreover, even the owners of new cars are not immune from valve burnout. There is also a similar problem with diesel engines. What are the VAZ-2110? Stuck saddles are usually the culprit. All this will be accompanied by a characteristic "tractor" engine rumble. must comply with the norm. If this is not the case, there is a risk of valve burnout.
A similar problem can happen on modern engines. The reason for this is the non-working hydraulic lifters. If oil does not pass through them, the gap will be set incorrectly. Among other signs, it is worth noting an incorrectly configured HBO (if installed on the car). When driving too lean, there is a risk of burnout of one or more valves.
Why is it dangerous?
The consequences can also vary significantly, ranging from the banal excessive consumption of fuel and ending with the burnout of the saddles. In more serious cases, damage to the piston and head occurs. How does this happen? A burnt exhaust valve, the symptoms of which will be discussed later, is broken into small pieces. As a result, part of the "plate" enters the combustion chamber. So there are scuffs and other damage. Long-term operation of such a car can lead to a complete replacement of the motor.
Signs of a burnt valve
On the VAZ-2110 and other vehicles, this malfunction will be accompanied by engine tripping. You will feel as if one of the cylinders has stopped working. Traction will also be significantly reduced, fuel consumption will increase.
What to do in this case? If the valve is burnt out, symptoms of a malfunction will be accompanied by low compression. The chamber will not generate the necessary pressure to push the piston. Therefore, first we take a compression tester in our hands, unscrew the candles and insert them one by one into each cylinder. It is worth noting that compression readings are very different on diesel and gasoline engines. In the first case, this parameter is at the level of 23-27, in the second - 10-12. But there are exceptions. For example, on derated engines (of the old Soviet production, which are designed for the 72nd gasoline), this indicator is 6-7 points.
It is worth noting that low compression can cause a worn-out cylinder-piston group. In this case, the valve will be in normal, working condition. But how to make sure the measurements are accurate? To do this, experts recommend pouring a little oil into the cylinder through the candle well. Use a medical syringe. It is important that the oil matches the parameters of the factory (or what was previously filled in).
After that, we install a compression gauge and call an assistant to scroll the starter at your command. The essence of the method is very simple - due to its viscosity, the oil will close the cavities in the cylinder walls. So we exclude the case of worn rings. If the compression readings are below normal with oil, then the valve is burned out. The signs are visible.
Checking candles
If the right oil or syringe is not at hand, you can determine the malfunction by the nature of the wear of the candles. To do this, they should be unscrewed from the seat and carefully inspect the condition. The candle will be dry, without oil deposits. Also, air or blue smoke will come out of the motor breather. If this is a relatively new motor and signs of a burnt valve have been confirmed, then most likely you have rings stuck.
How to avoid the problem?
The main cause of burnout is the work of the part in the mode of increased loads. The operating temperature of the valve is about 600-650 degrees. Clearances should be checked to prevent overheating. Due to the small distance, friction occurs and, as a result, overheating of the valve.
Signs can also point to poor quality fuel. On carbureted cars, the mixture is manually adjusted. It is important to prevent too much. The same applies to cars with LPG. There are two main generations:
- Second.
- Fourth.
In the first case, the mixture is adjusted mechanically by adjusting the "greed" tap. It is very easy to adjust it - we turn the valve until the car starts to stall. Then back off 1-2 turns. This is the most optimal setting. In the case of the fourth generation HBO, the setting is done programmatically, by specialists.
If the valve is burned out, when buying, pay attention to the quality of the product. A defective item will not last long. On a quality valve, various risks, scuffs and other flaws are excluded. The part itself is inexpensive, but with the installation you will have to sweat a lot. Indeed, to replace it, it is necessary to “throw off” the head of the block and carry out further grinding of the seats.
Conclusion
So, we found out why the valve burns out. The symptoms are mainly reduced to tripping - one of the cylinders will not work properly, since the mixture immediately evaporates to the outside. To prevent re-burnout, you should properly adjust the carburetor or LPG, as well as monitor valve clearances. If a characteristic clatter is observed, then the gap is set incorrectly or the hydraulic lifters were clogged.
The following symptoms of valve burnout are distinguished, which signal the driver that it is time to start diagnosing and repairing:
- the engine is unstable (troit);
- loss of power, throttle response;
- pops can be observed both in the exhaust system (muffler) and in the intake manifold.
Why do valves burn out?
Valve burnout is usually caused by one of the following problems:
- improperly adjusted valve clearance;
- low-quality gasoline or inconsistency of the octane number of the fuel with the recommended one;
- ingress of scale, a metal particle through the air and sticking it to the valve seat or the adjacent edge of the valve;
- excess fuel;
- the occurrence of soot on the valve due to hardened or torn valve stem seals, which leads to the passage of oil, which eventually burns on the valve, bakes, which prevents the valve from cooling during its opening;
- valve guide wear;
- weakening the desired elasticity of the valve spring;
- valve seat damage or wear;
- malfunctions in the engine cooling system, which leads to an increase in temperature;
- failed hydraulic compensator;
- cylinder ring wear.
Solution
When the car owner was able to find out that the valve had burned out, and determined the cause of what was happening, it was necessary to proceed to repair. First you need to replace the burnt-out valve with a new one, grind it in, if necessary, replace the guide sleeve and the valve stem seal. It is also necessary to eliminate the cause of burnout, otherwise the problem will quickly return with further operation of the car.
If an incorrectly adjusted thermal clearance of the valves is found, then it should be corrected. For this, special adjusting bolts and washers are used. On some engines, the clearance is adjusted automatically using hydraulic lifters. But if the hydraulic compensator is out of order, then the valve may burn out. In this case, after replacing the valve, the hydraulic compensator is also changed or repaired. Only collapsible hydraulic lifters are subject to repair.
If the problem is low-quality fuel, then you should get rid of it, and in the future fill in only high-quality gasoline. It is also important to comply with the octane number that is set by the manufacturer.
In case of an excess of fuel, it is necessary to eliminate the cause that causes it. On injection engines, the cause most often lies in the nozzles, they need to be washed or replaced. If we are talking about a carburetor engine, then you need to adjust the fuel level in the carburetor float chamber.
If the valve spring is worn out, it must be replaced with a new one. In the event of malfunctions in the engine cooling system, leading to severe overheating and burnout of the valves, it is necessary to eliminate them. For example, you may need to repair or flush the main radiator, replace the fan on sensor or the fan itself, replace the thermostat, tighten the pump drive belt.
If, in the course of searching for an answer to the question of how to determine a burned-out valve, wear of the cylinder rings was revealed, then an overhaul of the engine may be necessary. This process eliminates all excess wear and cylinder ellipse.
