Replacement of piston rings

The need to replace the piston rings may arise as a result of a single fault and severe wear of the rings themselves, and be included in the general complex of works on repair or tuning of the engine. Replacement of piston rings without boring of the block of cylinders or selection of piston rings on the size already after carrying out this operation provides a number of exact measurements by means of a micrometer and an inside gauge. Also, the correct installation of piston rings on the piston requires compliance with certain conditions and recommendations.

For optimal selection it is necessary to take into account not only the size of the piston rings in the table and the interchangeability of parts, but also the material of manufacture. In addition, special attention will need to be paid to the issue of thermal gap and a number of other features.

We also recommend reading the article about it, how to choose piston rings by size. In this article you will learn about the subtleties and nuances of self-selection of piston rings for gasoline or diesel engines.

Let's add, that the fact should be taken into account separately during the selection, that in the cylinders, which have a chrome coating on the mirror, the use of chrome-plated piston rings is prohibited.

Purpose and structure of piston rings

To better understand the nuances of fault diagnosis and replacement of piston rings, you must first consider their structure and purpose. Piston rings provide the necessary tightness of the combustion chamber (superstructure space) in the process of piston reciprocating movements. Rings happen:

• compression - upper (first) and the second (average, intermediate) ring;
• oil removal ring (lower);

Compression rings do not allow gases from the combustion chamber to enter the crankcase. Oil removal rings remove oil from the cylinder walls and prevent oil from entering the combustion chamber. The rings are slightly rounded and not solid, since they have an incision. This incision is called the piston ring lock. Also piston rings provide to 50% heat dissipation and effectively cool the piston. Excessive heat is transferred to the cylinder walls through the rings. For this reason, special requirements are placed on the materials of the rings, since they are prone not only to mechanical, but also temperature loads.

Piston rings are steel or cast iron parts, which have a certain elasticity and are able to spring. These rings are mounted on the piston head, that is, at the top. The head has special grooves for installing piston rings. The piston rings are additionally covered with an alloying material, which provides the details with the increased durability and adds resistance to wear. The end part of the rings has a special shape of the "barrel", and also covered with a special antifriction alloying composition.

On the end of the rings, which is in contact with the walls of the cylinder, tin or copper is applied as a coating. The application of this material is due to the task of quality grinding (part-time work) piston rings after the assembly of a new engine or overhaul of the engine. Let's add, that piston rings are not specially made of high-strength alloy steel, as such rings will not be able to grind normally in the engine cylinder. For this reason, engineers and manufacturers always maintain a certain balance to achieve the required strength of the rings, while maintaining the ability to work part-time. The solution was the above application of alloys on the surface of the part.

Signs of wear of piston rings

To understand, whether to change piston rings, it is necessary to study the symptoms, which directly or indirectly indicate the need for such replacement. Let's note at once, that you should not count on that amount, which was first voiced by a mechanic or car service in response to a customer question, how much does it cost to replace the piston rings.

The point is, that change only the piston rings and ??it is often not possible to solve the problem completely, because after opening the motor, additional hidden defects are usually detected. For this reason, you need to be prepared in advance for the more serious costs of repairing the engine.

The impending replacement of piston rings is determined by the following features:

• the engine loses power;
• the car starts very badly "cold";
• in some cases the motor hardly starts "on hot";
• there is an increased consumption of engine oil;
• the engine smokes blue or gray smoke;
• fuel consumption increases;

The compression index depends on the general condition of the rings and the entire CNG, by which you can determine the state of the engine. Usually with the above symptoms, the compression in the cylinders is reduced, crankcase gas pressure increases.

We also recommend reading the article about it, how to measure the compression in the engine. In this article you will learn about the features and available ways to measure engine compression with your own hands.

Power loss, increased fuel consumption and difficult start-up are often the main reasons, which force the owner to change the piston rings or make a comprehensive repair of the engine. The power unit with faulty rings starts badly, especially after downtime in the cold season. When driving under load, such an engine does not "pull".

Malfunctions of piston rings can be caused by natural wear, as well as engine overheating. In the second case, even on a new motor, the rings lose their properties and cease to perform a direct purpose. Box-type oil rings are the most prone to overheating.

Significant consumption of engine oil often occurs because of this, that the worn oil removal ring does not remove the proper amount of oil from the cylinder walls and actively leaks oil due to leaks in the combustion chamber. The result is coking and engine smoke. Also, the remnants of unburned oil in the engine actively contaminate the exhaust system, disabling filters and catalysts. The problem is even more complicated.

To accurately diagnose the state of the CHP compression measurements must be supported by analysis of color and exhaust gases. The point is, that the deterioration of the quality of the seal by the piston rings can be compensated by engine oil. In this case, the compression ratio is close to acceptable, while oil consumption will still be increased.

Remember, operation of the engine with worn out rings forces wear of a cylinder mirror considerably to progress. For this reason, the piston rings must be replaced as soon as possible after the fault has been identified. This recommendation will help to avoid increasing the cost of further engine repairs.

Increased fuel consumption in the case of problems with piston rings occurs as a result, that the compression is reduced and the power is dropped. At the same time, the driver continues to drive at the usual pace, pressing the accelerator pedal harder to compensate for losses. As a result, the enriched fuel-air mixture enters the cylinders, which burns in full. Spark plugs in such conditions are often filled with fuel.

Another unpleasant point is the ingress of gasoline or diesel fuel through worn piston rings into the crankcase and the subsequent mixing of fuel with engine oil. The oil in the lubrication system is diluted, loses its protective and other useful properties, and wear of the loaded details of TsPG and KShM at the same time strongly increases.

Let's add, that today it is quite common practice to use additives for cleaning piston rings in oil or fuel. Also, owners sometimes pour into the cylinders of the so-called decoking engine. This is done for that, to clean the scale in the combustion chamber and try to restore the mobility of the bearing piston rings to increase compression.

It should be noted, that at emergence of obvious signs of malfunction (heavy smoke, high oil consumption, low compression, etc.) the additive instead of replacing the piston rings is either a temporary measure, or does not help to correct the situation.

How to properly install piston rings

To answer the question, how to replace piston rings without removing the engine, it is necessary at the initial stage to make a defect in the CHP. To do this, you will need to remove the cylinder head, then an assessment of the general condition of the pistons and cylinder walls.

This is done to detect possible defects (bullies on the walls, wear, destruction or melting of the piston, etc.). Let's add, existing engines, on which it is impossible to assess the condition of the CHP without removing the pallet. Often there is a high probability, that one replacement of rings with new ones may not be enough, as at detection of serious development it is necessary to bore the block of cylinders.

Note, that the installation of new compression rings without removing the engine in worn cylinders is not recommended. The point is, that in the course of operation on a mirror of the cylinder the so-called step is formed. After installation of new details there is a high probability of breakage of piston rings about the specified step, requiring re-disassembly and more expensive engine repairs.

Moreover, the rings wear out like a mirror of the cylinder, and the inner surface of the piston groove. For these reasons, new piston rings, which are put without replacement of pistons and repair of cylinders, or do not grind at all, or grinding is very slow and inefficient.

Given the above, the best option is to bore the cylinder block, performing honing of cylinders, then the installation of new repair pistons and piston rings. It is not possible to make such repairs without removing the engine. At the same time, the positive results of repairs with the removal of the motor are much more predictable.

In any case, the rings on the removed engine are changed or the piston rings are replaced without removing the unit, the general procedure is as follows:

• remove the cylinder head;
• perform cylinder head defect, BC and CPG;
• perform appropriate measurements to determine the required size of the piston rings;
• buy piston rings, which are suitable in size and performance;
• drain the engine oil and open the crankcase pan;
• if necessary, remove the oil pump;
• then you need to remove the scale at the top of the cylinder;
• then unscrew the heads (cover) connecting rods and push them up (mark each head, as at the subsequent assemblage the head of a rod has to correspond to that rod, where it was taken).

To deal with it, how to properly put the rings on the piston, follow the further recommendations. The piston rings themselves change relatively easily. To remove the old rings, you need to spread the edges of the ring in the area of ​​the lock until then, until the ring comes out of the groove on the piston. This procedure can be performed using special forceps, and with a small flat screwdriver.

After it is necessary to remove from the grooves on the piston soot. If you do not reject this soot, then after installing the new piston rings the piston will be difficult to install back into the cylinder. You can use an old compression ring to remove scale from the piston grooves, which for convenience breaks into two parts.

After completing the procedure for cleaning the grooves of the piston, you must study the instructions for installing the rings, attached to the new kit. This instruction contains the procedure for installing the piston rings on the piston, that is, the sequence of their correct installation and the order of location. The top or bottom is also indicated, according to which the piston rings must be installed with the upper or lower location of a special label.

Care must be taken when installing the rings on the piston, as the middle compression ring and the lower oil removal ring are characterized by increased fragility. As for the upper ring, this element is stronger than others, but also requires the right approach when installing.

Installation of rings on the piston

Excerpts from the installation instructions for Mahle piston rings will be discussed below, as well as added some tips and tricks.

1. After cleaning the grooves from soot you need to make sure, that there is no damage on their side surfaces and radii.
2. Use special collet fittings to mount the rings.
3. Installation of rings must begin with the lower piston ring. Avoid unnecessary effort, to exclude possible deformation of rings.
4. Before installation, find the marking on the ring in the form of the inscription TOP (from English. "Top"). Rings with such markings should be placed towards the bottom of the piston marked side.
5. If the rings are installed, which have expander springs, then the joint in the form of the ends of the spring with a wire insert is placed taking into account the recommended offset on 180 ° degrees relative to the joint of the piston ring. If there are Teflon shirts in the expander springs, this element must be in the area of ​​the ring joint.
   Rings, consisting of several lamellae, after installation of a spring it is necessary to arrange taking into account that, that the joints of these slats were directed to the hole of the piston pin. When placing the upper lamella, the ends of the spring must be fixed.
6. If the piston has special clamps in its grooves, which prevent the rings from turning, then the joints of the piston rings must be on the pins for fixing.
7. After completion of installation it is necessary to check up a backlash of lateral surfaces. If the figure is within the limits of 0.100 mm, then such a gap is allowed. Detection of increasing the gap from the maximum allowable indicates the need to purchase and install new pistons.
8. The degree of wear of the cylinder mirror must be taken into account during installation. Such wear is considered acceptable in value 0.100 mm (taking into account the diameter of the cylinder). If the gap is larger, then the cylinder block requires rebinding or boring under repair pistons.

As mentioned above, Increased attention during installation should be paid to both mutual location and orientation, and the type of piston rings. Oil-removing rings differ from compression rings by a unique U-shaped profile, and also have in their design an expansion spring.

The second compression ring is equipped with a scraper-edge, as it is partially involved in the process of oil removal in parallel with the operation of the oil removal ring. The presence of an edge on the piston ring usually indicates this, that such a ring is installed taking into account the lower location of the edge. Careful dosing must be made when installing the rings on the piston. Otherwise, the piston rings can be easily broken.

We will also add, that after installation of rings on the piston and its placement in the cylinder rings carry out dense adjoining to cylinder walls. The so-called thermal gap is formed in the locks. Then use a probe to measure this gap, which should not exceed the figures 0.25-0.45 mm. If the specified gap is less, then the ring will not be able to fit properly in the groove of the piston. To solve the problem, you can use a file and carefully remove excess millimeters.

As for the correct location, to prevent gases from breaking through the ring locks you need to know, how to put piston rings. When installed correctly, the rings are put on the piston, taking into account the shear in a circle. An example is the installation of 3 piston rings. At such installation locks need to be put so, so that each of the locks is located across 120 ° relative to another.

Run-in of the engine after replacement of piston rings

Regardless, only the piston rings were replaced or the engine was overhauled, the motor needs running-in. This is due to the need to forge new details. Run the engine after replacing the piston rings should be similar to running the engine of a new gasoline or diesel car.

After replacing the rings, the motor can be operated in heavy-duty operation (high speeds while driving, simple at idle, driving at low speeds in high gears, etc.) minimum 3-5 thousand. Km. You should also not start the trip without pre-warming the engine.

Next, consider the views of experienced car mechanics and answer a general question, how much you need to run the engine after replacing the piston rings. The statement is quite common among experts, that for complete grinding of the rings will take about 10-15 thousand. Km. Hence the conclusion - after a minimum run-in of the car after overhaul of the engine or replacement of rings (to 5 thousand. Km.) It is highly undesirable to spin the power unit above the average speed range even closer 5 or even 10 thousand. Km. mileage.

Let's summarize

In a working atmospheric gasoline or diesel engine, which is operated under normal conditions, the average resource of piston rings can be from 150 to 350 thousand. Km. Highly forced "atmospheric" and turbocharged engines (especially gasoline) may need to replace the rings when running close 100 thousand. Km. The averages are given accordingly, that the service life of piston rings is strongly influenced by such factors:

• modes of operation of the internal combustion engine;
• quality of engine oil;
• efficiency of lubrication systems, cooling, etc..

Example, the piston rings may fail immediately if the engine overheats. Wear of rings strongly increases at operation of the motor on not corresponding recommended, dirty or just low-grade oil. Problems with starting a cold engine or unstable operation of the unit at idle can make the driver "gas" on a cold engine, as a result, the piston rings wear out very strongly and quickly.

Finally, let's add, that if the piston rings have been replaced and the engine does not start without visible ones ??reasons, then the destruction of the rings is possible in the case of unprofessional installation of new parts in the cylinders without repair. In this case, a common problem is that, that after replacement of piston rings there is no compression, which is necessary for compression of the mixture and normal cold start. Such a malfunction may be the result of incorrectly selected repair dimensions of parts or other errors during the repair.

In that case, if the car smokes after replacing the piston rings, then the intensity of the smoke and the color of the exhaust gases should be assessed. At the very beginning of the process of forging piston rings, the appearance of blue-gray smoke is allowed, then the intensity of smoking and color should be gradually normalized. If after the first 1-3 thousand. Km. this does not happen, then it is necessary to re-diagnose the power unit.