The piston and cylinder of an internal combustion engine have close dimensions, however, no matter how high precision they are made, there is still a gap between them, through which gases resulting from the combustion of the working mixture could freely pass into the crankcase, and from the crankcase into the chamber combustion engine oil would get in. Piston rings are used to prevent these extremely undesirable phenomena.

They are open rings, set with a small gap in the piston grooves intended for this purpose. According to their purpose, they are divided into two groups:

• compression, the task of which is to prevent the breakthrough of gases from the combustion chamber into the crankcase;
• oil scraper, designed to remove excess engine oil from the cylinder walls.

Compression piston rings have an outer diameter slightly larger than the cylinder diameter. In order for the part to fit inside, a cutout called a lock is made in it. The surface of the compression ring is made even, without any grooves. Oil scraper rings, unlike them, have through slots designed to drain oil.

The number of rings installed on one piston may vary. At the dawn of the automotive era, when engines were slow to cope with compression losses as best as possible, their number reached seven. In modern engines, as a rule, three are used for each piston: two compression and one oil scraper. In sports cars with high-speed forced motors, engineers quite often limit themselves to two at all.

What materials are used to make piston rings

Various materials are used in the manufacture of rings, such as cast iron, stainless steel, chromium and molybdenum. Cast iron combines low cost and fairly high performance, which caused its wide distribution.

Stainless steel contains a large amount of chromium to increase heat resistance and wear resistance. Thanks to this, stainless steel rings, like chrome ones, resist high temperatures better than cast iron ones. Since the first compression ring operates under conditions of lack of lubrication, this factor must also be taken into account when choosing a material for it. As well as possible, the same chrome is suitable for coating. Chrome-plated products resist abrasion much better.

Molybdenum is used as a coating for the working part of the rings in order to increase their resource. In addition, molybdenum piston rings run in faster to the cylinder walls, which is especially important if they are replaced during an engine overhaul.

Piston ring anatomy

You should not think that the same metal is used for all the rings in the kit. The material used is mainly influenced by the position of the piston rings on the piston. Since all piston rings operate under different conditions, the requirements for the alloys from which they are made are different.

First compression ring

The first compression rings are subjected to the most severe conditions, so they are subject to the highest requirements for heat resistance and wear resistance. Most often they are made of cast iron with a molybdenum anti-wear insert.

At first glance, all compression rings look the same, but their configuration can vary significantly. For example, the top may be slightly twisted. As a result, only its edge is in contact with the surface of the cylinder, and not the entire surface. As a result, friction losses are reduced and run-in time is shortened.

Another type is compression rings with an L-shaped section. Their distinguishing feature is the ability to change the degree of compaction depending on the pressure exerted by the working gases on the back of the large L-shaped protrusion. Under pressure, they expand, improving compression (during the compression stroke), when the pressure decreases, the diameter, on the contrary, decreases, while reducing friction and wear of parts. Which of the rings is better, everyone decides for himself, since everyone has their own advantages.

Second compression ring

Its working conditions are less stressful, so the requirements for the material from which it is made are less stringent. The second compression ring performs a dual task:

1. provides additional sealing, trapping gases that have broken through the first;
2. works like a scraper, preventing engine oil from entering the combustion chamber.

Often the second compression rings are truncated cone shaped, i.e. The diameter of the top is smaller than the diameter of the bottom. Thanks to this design, when the piston moves down from the cylinder walls, oil is removed.

Both compression rings have only one correct position for installation, they must not be turned over in any case, otherwise they will not work correctly. To prevent errors during installation, they are marked on their upper side, for example, "T" or "TOP".

Oil scraper rings

They are installed under compression. Unlike the latter, their surface is not continuous, it has windows designed to drain engine oil. In modern engines, oil scraper rings are installed one for each piston, in the past they were installed several, especially in engines designed for stationary use.

Selection of spare parts

When performing an engine overhaul, it is necessary to choose the right piston rings, since an incorrect selection will either lead to a lack of the necessary compression, or to jamming of the pistons in the cylinders, followed by the destruction of the rings and the formation of numerous scoring on the pistons and cylinder walls. Consider, using the example of the VAZ-2111 engine, how to choose the right parts.

There is a table of repair sizes for pistons and rings, with which it is quite easy to choose the appropriate diameter of parts. The basic diameter of the cylinders of the VAZ-2111 engine is 82 mm, the repair pistons have an increased diameter: by 0.4 mm for the first repair and by 0.8 mm for the second. Rings for repair dimensions also have an increased diameter, and they are marked accordingly.

In general terms, the overhaul process of the VAZ-2111 engine looks like this: the cylinders are bored to the first repair size, while leaving a small allowance for honing. Then the old pistons are replaced with new ones of increased diameter, and piston rings of the first repair size are mounted on them.

A repair size table exists for all engines, and it will not be difficult to choose the right diameter for any engine, whether it is a VAZ or Subaru engine.

Which rings are best

The question of which piston rings is better to purchase for replacement haunts many car owners. With so many to choose from, it's not easy to make a choice. You can answer this way: if the purpose of the replacement is to restore the normal operation of the motor, standard ones are quite enough, but if the owner wants to improve engine performance, it is better to pay attention to more “fancy” products, for example, chrome or molybdenum.

Many motorists are interested in how to identify a problem with piston rings in a timely manner and what are the main signs of a malfunction of these parts. In order to understand this issue, it is necessary to clearly understand the purpose of the compression and oil scraper rings of the engine, the features of their design and operating conditions.

Design features and purpose of engine piston rings.

The piston rings of an automobile engine perform 3 main tasks:

1. Prevention of breakthrough gases from the combustion chamber into the crankcase.
2. Removal of heat from the piston heated by the exhaust gases into the cylinder walls.
3. Ensuring lubrication of parts of the cylinder-piston group and preventing (or at least minimizing) oil from the crankcase entering the combustion chamber and, as a result, increased oil consumption.

In most modern engines, these functions are performed by three piston rings:

The upper compression ring is responsible for sealing the combustion chamber and is subjected to very high loads, as it takes up most of the pressure of the exhaust gases during combustion. In addition, the rings operate at elevated temperatures, which affects their lubrication and wear conditions, which ultimately leads to increased oil consumption. To ensure resistance to high temperature and power loads, the upper rings are made of high-strength cast iron alloyed with molybdenum, nickel and chromium.

The middle oil scraper ring, in addition to the sealing function, also controls the lubrication of parts and prevents increased oil consumption. During the piston stroke from top dead center to bottom dead center, the ring removes oil from the cylinder walls. To achieve this function, the middle rings are specially shaped to allow oil to be skimmed off the walls on the downstroke and passed through on the upstroke, preventing oil from entering the combustion chamber. Since these rings are less loaded than compression rings, they are usually made of a less durable material - gray alloyed cast iron with lamellar graphite.

As you might guess from the name itself, the main task of the lower oil scraper ring is to remove oil from the surface of the cylinder and drop it into the crankcase through holes or grooves in the piston groove. Since the functions of this ring are different from those performed by compression rings, its design is also significantly different.

Currently, the most widespread are 2 types of oil scraper rings:

1. box-shaped with an expander spring;
2. type-setting, which consists of two disks and a two-functional expander.

The main requirements for these rings are good running-in against the cylinder walls and high pressure on them, which ensures effective removal of lubricant and prevention of increased oil consumption. Depending on the type, oil scraper rings are made of gray alloyed cast iron or carbon steel. For effective work in tandem with a cast-iron sleeve, their surface is chrome-plated.

The main signs of piston ring wear

When the upper compression rings are worn, as a rule, the compression in the engine decreases, which manifests itself in a deterioration in the accelerating dynamics of the car, and if the rings are not worn on all cylinders, then such an engine runs unevenly. In order to determine in which cylinder the rings are worn out, it is necessary to measure the compression. In a serviceable gasoline engine, it should be 11 - 13 bar, in a diesel engine - from 23 to 40 bar.

When worn oil rings

Wear or failure of oil scraper rings is manifested in increased oil consumption under normal operating conditions. Also a sign of wear on the rings is the presence of black smoke from the exhaust system and the crankcase ventilation system (breather). The reason for this is the burnout of engine oil that has entered the combustion chamber.

One of the possible signs that may indicate wear of the oil scraper rings is the contamination of the candles with oil, but this also happens if the oil valve caps are worn out. To accurately determine the cause of the malfunction, disassembly of the engine will be required.

In most cases, in modern internal combustion engines, the service life of oil scraper rings is 150-200 thousand kilometers, and in some engines even from 300 to 500 thousand. However, if the car is operated in difficult conditions or its owner does not change the oil in a timely manner, then their replacement will be needed already after 50 thousand kilometers. In this regard, when deciding to replace compression and oil scraper rings, you should not be guided only by the mileage of the car.

What to do when the rings are worn?

In order to choose a way to solve the problem, you need to find out why it arose. The occurrence of the above symptoms may be caused by wear or breakage of compression and oil scraper rings, or if they are coked and stuck.

In the first case, it will be necessary to disassemble the engine and install new parts instead of damaged ones. In this case, all mating parts should be carefully inspected, since if the rings break, scoring may occur, which can only be eliminated by overhaul.

If there is an assumption that the piston and oil scraper rings are stuck, then a special additive can be added to the oil. But this method is used, as a rule, for preventive purposes.

Piston ring-related malfunctions occur quite often in practice. Therefore, in order to prevent the occurrence of serious consequences and, as a result, high repair costs, it is necessary to recognize their first symptoms in time and take appropriate measures.

Evgeniy Shuba, Ph.D., Lecturer, Department of Engines and Heat Engineering, National Transport University

Piston rings installed in the piston group simultaneously perform several important functions for the engine.

The purpose of the rings

Combustion chamber gas seal (space above the piston)
Removal of part of the heat from the piston surface of the cylinder
"oil management", i.e. removing excess oil from the walls of the cylinder and at the same time providing lubrication of the rings themselves and the cylinder.

On most modern engines, both gasoline and diesel, a set of three rings is installed. The two top rings are compression rings and the bottom oil scraper ring.
Although the middle ring is often assigned a dual role, where it not only serves to maintain compression, but also partially serves to remove oil, but this will be a separate article.

Oil scraper rings of modern engines are installed in two types:

Box ring with expander spring
Stacking ring consisting of a two-functional expander and two steel discs

The box ring is by and large an oil control ring, while the type-setting ring is purely oil scraper.
The box ring gives a slightly higher oil consumption due to the passage of part of it being close to the dead points, but it provides lubrication of the piston and cylinder. This is due to the detachment of the "crest" of the ring from the cylinder wall at the moment of "relocation" of the piston.

There is no such disadvantage oil scraper ring, since its disks are not rigidly connected to each other and the contact of the disk with the cylinder mirror always remains constant.

This is achieved due to the fact that the disks has a small thickness, about 0.50-0.63 mm, which allows them to “adapt” well to the surface of the cylinder, compared to a box-shaped oil scraper ring.

This design oil scraper ring allows him to remove almost all the oil from the cylinder walls, sometimes even leading to starvation of the piston-cylinder pair.
For this, the design of the middle compression ring has been specially changed, which is able to hold part of the oil for lubricating the rings, piston and cylinder above the oil scraper ring.

In diesel engines, where the operating conditions of the piston group are much tougher, the requirements for lubrication are increased, mainly box-shaped oil scraper rings are installed.
Japanese and American gasoline engines are mainly equipped from the factory stacked oil scraper rings, and European manufacturers prefer box-shaped oil scraper rings.

The height of the scallops with a large wear of the box ring becomes minimal, and sometimes they wear out completely, which leads to an increase in the gap in the ring lock and high oil consumption.
Stacked oil scraper ring not subject to this, since the increased gap in the lock overlaps another disk, which is separated by the ring lock in the opposite direction.

When replacing rings, without performing any grinding operations, the option with stacked oil scraper rings will be more reliable. Usually these rings are more expensive than box-type oil rings, but the price is justified and will pay off handsomely.

Oil scraper rings and caps are sometimes called the most important elements of the engine. Let's figure out what these parts are, where they are and how the replacement is made - in order to provide first aid to your iron horse at any time.

Getting to know oil scraper rings

So, piston rings, which include oil scraper rings, play a huge role in the device of the vehicle. This kit consists of three elements: upper compression, compression-oil scraper and lower oil scraper ring. Many parameters depend on their performance: this is accelerating power, exhaust toxicity, starting properties of the engine, and oil. So keeping an eye on them is very important.

So, the main function of such rings is to remove heat from the piston. Otherwise, various defects will appear on it - burnouts, scuffs - which will lead to incorrect operation. The part will jam in the cylinder. Thanks to them, the tightness of the combustion chamber is ensured, and therefore, the movement of gases from the cylinder to the crankcase and vice versa is minimized. In addition, the lubrication of mating elements is regulated. After all, both oil starvation and its excess lead to negative consequences. And the flow of liquid into the combustion chamber should be very limited or completely excluded.

Before talking about malfunctions, replacement and decoking of oil scraper rings, let's pay a little attention to their design features. One-piece parts today have lost their popularity and are even discontinued. Due to their increased rigidity, they cannot adhere to the surface sufficiently and remove oil thoroughly.

There are parts consisting of two and three parts. The first kit includes the ring itself and the coil spring. Their advantages include increased flexibility, due to which a snug fit to the walls of the cylinder is ensured. The spring is so pressed against the inner side of the ring that the structure is solid. Three-piece rings consist of a spacer spring and two steel plates. Basically, they have found their application in gasoline engines. The pluses include the most snug fit around the entire perimeter.

The working day of oil scraper rings

The greatest load falls on the compression ring, so it is made mainly from special alloyed materials. Also, a wear-resistant coating is applied to its surface, because this element must withstand gas pressure and high temperature. So, as you approach the upper critical point, the amount of lubricant decreases, and an increase in pressure in the cylinder contributes to a tighter fit of the ring to the walls. The speed of movement also decreases, and a complete stop completely leads to a break in the oily film. In other words, the part operates in dry friction mode, which means it wears out very quickly.

The middle ring experiences much less stress. It is made from cast iron. For uprated engines, a wear-resistant coating is applied to the compression and oil scraper elements. The fact is that the castle has increased pressure. From the name it is clear that they perform not only compression functions, but also take part in the management of lubrication. To exclude the possibility of oil entering the combustion chamber, the outer surface has a conical shape with an inclination angle of not more than 0°80’. The main task of such elements is to remove oil from the walls during the downward stroke and prevent it from entering the combustion chamber during the upward stroke.

The last elements are only responsible for removing oil and draining it into the crankcase. To cope with the task as efficiently as possible, the design provides for two belts, each of which removes oil residues. As a result, liquid collects both between these belts and on the lower edge of the part. To eliminate it, the lower caps have oblong slots or holes through which the substance is removed to the reverse side. Further, it already falls into a special pan or on the outside of the piston.

Seizure or wear - when is it time to check the condition of the rings?

As you can see, the operating conditions of piston caps and rings are not easy and therefore natural wear cannot be avoided. Typically, the kit is enough for 150 thousand kilometers, although some car owners claim that their engines go up to 500 thousand km. But we can talk about such indicators only with the correct operation of the car, otherwise you will have to think about repairing the engine much earlier. The use of low-quality or unsuitable oil and its untimely replacement will negatively affect the condition of the rings, which will bring them closer. In addition, it is necessary to monitor the condition of the air filter, especially if you have to constantly drive through very dusty areas. The correctness of the fuel filter is also important.

It is advisable not to overheat or overload the engine itself. The formation of soot in the piston grooves leads to the occurrence of oil scraper rings. In this case, the piston does not fit snugly enough to the cylinder and the car cannot develop the necessary power. You can delay the occurrence of the oil scraper ring as much as possible. Avoid short trips in winter, as the engine does not have time to warm up to the desired temperature. It is very dangerous to give excessive loads during this period. If there is not enough lubrication in the system, overheating will occur. It will lead to jamming and the formation of various defects on the surfaces of the piston and cylinder. As a result, the caps may be completely damaged, or the partitions between the grooves may be destroyed. Dangerous for the car and constant downtime in city traffic jams.

You can determine the need for repair or replacement by the following signs of wear on the oil scraper rings. Oil consumption will increase significantly, blue smoke may appear - during the start of movement after a short stop, for example, at traffic lights. Besides, alarming signs of wear - leakage and evaporation of oil through seals, seals (caps) and in other places. Pay attention to the color of this liquid, if you just changed it, and it turned black, then replacing the seals is inevitable. Still follows, they must be clean, otherwise you will have to contact the service station or carry out repair work yourself.

So, if you find any signs of wear on your car, then you need to check the oil scraper rings. Diagnosis of caps is quite simple. It is necessary to disconnect the hose of the forced ventilation system. If the crankcase pressure is increased, then the point is the wear of the caps.

Decarbonization and its meaning

But is a complete replacement of parts always necessary, or is it possible to somehow extend their life? In the case of soot and the occurrence of rings, decarbonization often helps. Experienced minders share the following recipe for restoring such elements without dismantling. A mixture of acetone and kerosene is prepared in equal proportions. Then you should unscrew the spark plugs and pour the decarbonizer into the cylinder through the holes formed. We leave for 9 hours. After the time has passed, we install the candles in their regular places, start the engine and ride at maximum speed (10-15 km is enough). After a very desirable oil and filter change.

You can also purchase special oil scraper ring decarbonizers, especially since today there is no shortage of such chemistry. In principle, their use is similar to each other and to the previous method, but there are some differences, so be sure to read the instructions. Consider one of the schemes of decoking with a special liquid. We raise the front part of the front-wheel drive cars with a jack, for rear-wheel drive cars, respectively, the rear. We unscrew the candles and set the pistons to the middle position. To do this, you need to turn on the last gear and, scrolling the engine by the wheel, determine the position of the pistons. Then pour the decarbonizer into the spark plug holes. Deoxidation of soot usually occurs in 15 minutes, although do not forget to specify this time in the instructions.

To help the liquid decoke the entire surface, scroll the wheel, change the angle of rotation. But not continuously - they moved it several times, let it rest for a couple of minutes, then repeat the procedure.

To prevent breakdown of the ignition coil while cranking the engine, you should remove the central high-voltage wire and fix it somewhere in a safe place, while not forgetting to maintain a distance of at least 5 cm to the ground and the metal tip of the wire. The next step is to scroll the engine with the starter with the transmission off. 10 seconds is enough. This stage is necessary, because this is the only way to throw the remaining decarbonizer out of the cylinder. If this is not done, then after starting the engine, water hammer may occur, which is fraught with failure of the entire power unit. Decarbonization is completed, now it remains to return everything to its regular places and start the car. Do not be afraid if the engine does not immediately respond, help it with gas. Also, you should not be embarrassed by strong smoke from the exhaust pipe. Start the car and let it idle for another 15 minutes.

Step by step replacement - help for an amateur

Decarbonizing helps only in the case of soot, but if we are talking about wear, then only a replacement will save. It can be done by hand. We will need a special puller, a mandrel for pressing, a metal rod, we still cannot do without tweezers and a cracker. When purchasing new caps and rings, give preference to quality - look for original parts. Remember, if you get a fake, then you can enjoy the correct operation of the engine for only a few thousand kilometers. In addition, the coating of the upper rings is sometimes matched to the material of the engine. And the compression and oil scraper elements must match the material of the cylinder liner. If the replacement is made by cheaper analogues, then the result may turn out to be negative.

The next step in replacing oil scraper rings and caps will be the dismantling of components and mechanisms in order to provide access to parts. Remove the air filter first, then the fuel pump. Don't forget about the ignition distributor. To dismantle the drive housing for auxiliary units, it is necessary to disconnect the bolted connection, then remove the negative terminal from the battery, and the toothed pulley from the camshaft. Next, to get to the head cover, remove the mass drive. Lastly, the nuts securing the front and rear camshaft bearing housings are unscrewed.

The position of the camshaft key cannot be ignored, if it is not tight enough, then it must also be dismantled, otherwise it can be lost. Now access to the camshaft itself has become free, we take it out and the oil seal. Now we turn the part so that the piston is at TDC, and, having removed the candle, we insert a metal rod into the hole formed, otherwise the valve will fail. Then we compress the valve springs with a special tool and take out two crackers with tweezers. We press out the rings using the tool.

Now installation. We remove the springs from new parts so as not to damage them. Before installation, do not forget to lubricate the elements with engine oil. We press the part and put the springs in place. Installation of oil scraper rings should be carried out strictly in reverse order. When installing the middle ones, it is very important not to confuse the sides, otherwise the oil consumption will increase significantly.

Piston rings serve to pressurize the combustion chamber and remove excess oil from the cylinder walls. When designing an internal combustion engine, engineers invariably face the same problem - the piston bottom and cylinder cannot be the same diameter.

Wherein oil must not enter the combustion chamber. A massive piston will jam in the cylinder, even if it is slightly smaller in diameter, but a narrow flexible ring equipped with a movable lock will not. The use of rings proved to be the perfect compromise.

What are oil scraper rings?

Oil scraper rings prevent oil from penetrating the crankcase into the combustion chamber by removing excess oil from the cylinder wall. They are installed below compression. They, unlike compression rings, have through slots or consist of two scraper-type rings. On the pistons of some engines, composite oil scraper rings are installed, made of two steel disks and two spring expanders - axial and radial. An axial expander located between the discs presses them tightly against the walls of the piston groove. The radial expander presses the discs tightly against the cylinder. The collection rings adhere well to the cylinder surface and ensure low crankcase oil consumption.

Main functions and types

The oil scraper rings are installed at a level lower than the compression rings. In contrast to the one-piece structure of compression, they are made with through slots (made of cast iron), or composite with expanding springs (made of steel). Composite rings are one thin upper ring, one lower and two expanders (axial and radial). Depending on the type of piston and engine, a pair of oil scraper rings can be installed. This type of rings is produced three types:

- chrome-plated,

non-chrome,

Steel.

Sealing the expansion or combustion chamber; increase in compression, so that the engine can run and start.

Reducing the overall consumption of engine oil of the machine (for all four-stroke and diesel two-stroke engines); this must ensure sufficient lubrication of all sliding elements.

Keeping exhaust gases from getting into the crankcase. Removal of excess heat from the working piston, which prevents its overheating and normalizes heat transfer through the cylinder walls.

Where are the rings placed?

The location and type of piston rings depends on their usage profile. The complete set of rings for a solid piston will differ from the complete set of a composite piston, since the latter includes an intermediate second ring.

Before the direct installation of new parts, it is necessary to thoroughly clean the pistons and sleeves. In addition, in the process of dismantling the piston group, it is important not to violate the strict completeness of the parts. Experts recommend putting labels on their non-working surfaces for themselves. This will guarantee the normal operation of all parts of the engine control unit. List of piston rings for one-piece engine piston:

- The topmost compression ring is installed with a trapezoidal section without slots and twisting.

The second is a piece of rectangular section, equipped with a cut corner, which will ensure simple twisting. The presence of a conical cutout on various engines can be located both above and below.

The oil scraper part is located at the bottom.

Piston ring list for compound piston:

- A compression piece of trapezoidal section is installed on top, it is important that it be without slots and twisting.

Intermediate is a piston ring with positive twist and a tapered cutout along the top edge of the spare part.

An oil scraper is installed at the bottom.

What are the faults?

The main malfunction of piston rings is their wear during long-term operation. The resource of piston rings of domestic car engines is approximately equal to 150,000 km, or rather, the state of the connection between the piston rings and cylinder walls. The rings of modern vehicles from leading manufacturers can serve as up to 300,000 km, however, sometimes you have to hear from the owners that the engine of their car has already passed 500000 km. The mileage of the best trucks-tractors can be more 1000000 km.

But these runs can be significantly reduced by improper operation. Accelerated wear of the piston rings is caused by an untimely oil change in the engine, the use of an engine that is not suitable for this engine or contaminated oil.

Untimely replacement of the air filter and, moreover, operation of the car without an air filter at all or driving on dusty roads. The use of low-quality fuel or untimely replacement of the fuel filter. Difficult conditions include the constant operation of the car in city traffic jams. Short-term trips are very harmful for the rings, during which the engine does not have time to warm up to normal operating temperature, especially in winter.

It is not allowed to operate the engine with high loads until it is fully warmed up. The engine management system of some high-powered vehicles does not allow the engine to develop full power until the engine oil temperature reaches a set limit. It is the oil, not the coolant of the cooling system.

There are cases of rapid, avalanche-like destruction of piston rings. This may either be due to severe engine overheating or as a result of running the engine under conditions of insufficient lubrication. In such cases, jamming of the rings in the cylinder, the formation of scoring on the walls of the cylinder and the piston, the destruction of the piston rings and partitions between the annular grooves of the piston is possible. This condition of the engine is diagnosed quite easily.

A sign of unacceptable piston ring wear is increased oil consumption. If the engine of a small car consumes more than 0.5 liters of oil per 1000 km and at the same time when starting from a stop after a stop at a traffic light, blue smoke appears from the exhaust system, it can be assumed that the engine piston rings have unacceptable wear. In this case, an increased pressure of the crankcase gases of the engine can be observed, which can be determined by disconnecting the hose of the forced crankcase ventilation system. Also, oil leaks through oil seals, gaskets and other engine seals testify to the high pressure of crankcase gases.

For more accurate diagnosis, it is necessary to check the compression in the engine cylinders and check the condition of the cylinder-piston group using the compressed air leak method. Initially, the compression piston ring in the section had a fairly simple rectangular shape, but over time, the shape of the rings became much more complex. The ring has an outer (working) surface in direct contact with the walls of the cylinder, an inner surface directed towards the center of the ring circumference and two side surfaces, upper and lower.

As a result of the evolution of the engine, the shape of the ring section has ceased to be rectangular. To ensure greater durability of the ring, its faster grinding to the surface of the cylinder, to reduce the likelihood of ring coking in the piston grooves and to ensure other ring performance, the shape of the ring cut has become quite complex and very diverse.

The conical working surface is made to ensure easier grinding of the piston rings to the cylinder mirror during the engine break-in period. For the same purpose, twist rings are made. Rings that have grooves or chamfers on the inner diameter twist when compressed. Twisted rings reduce the ring's ability to radially vibrate and improve the removal of oil from the cylinder walls on the downward stroke of the piston, while leaving the required oil film on the piston's upward stroke.

A ring having a groove or a chamfer in the upper part of the inner surface, when compressed, takes a positive twist, that is, the outer surface rises. A ring having a groove or a chamfer in the lower part of the inner surface takes a negative twist during compression, that is, the outer surface goes down. Single-sided or double-sided trapezoidal piston rings reduce the possibility of ring coking in the piston grooves.

What to do if oil scraper rings lie?

What happens to an engine when piston rings stick? Let's deal with this issue, and at the same time see how this problem is solved on our own.

The occurrence of piston rings leads to a loss of their mobility. This happens due to the accumulation of soot from burnt oil, which strongly clogs the grooves in the piston, which leads to sticking of the rings inside the "nests". In this case, the seals between the piston and the cylinder are bound to deteriorate. The engine loses compression without developing the required power, since there is not a sufficient degree of compression of the working mixture. By the way, it is for the same reason that the engine will not adequately start in cold weather, since the rings are clogged with coke.

What follows next? The first thing that will indicate problems with the engine is increased oil consumption. Oil scraper rings suffer from soot, as they work like a scraper. Often, piston ring sticking occurs during short trips within the city, when the engine does not have time to warm up.

Another reason for the occurrence of rings is low-grade (fake) oil. The quality of the oil is a very important aspect, since there will be soot or not - it depends on the quality of the product. So, for example, if you use questionable butter, it will burn like margarine in a pan. Therefore, buy the oil that is recommended specifically for your car by the manufacturer.

And now the question is: how to get rid of soot? There is advice from experienced master minders who have already "eaten the dog" in this matter. In order to remove carbon deposits from piston rings, use the following recipe. Turn out the candles. Fill each cylinder with a mixture that consists of 50% kerosene and 50% acetone. We leave the engine overnight. This mixture provides softening of soot.

The next morning we twist the candles into place and start the engine. On a straight section of the track, you should drive the car at maximum speed, 15 kilometers. Oddly enough, such a simple method will allow you to clean the piston rings from dirt and restore their mobility without resorting to disassembly. But do not forget to change the oil and filter: the old oil is already clogged with washed off soot after applying the cleaning mixture that you poured into the cylinders overnight.

And the last. In order to avoid the formation of soot in the future, only two rules should be observed. Firstly, even if you rarely leave, still warm up the engine at least once a week and “walk” your car a little. And secondly, use only high-quality oil.