Correct installation of piston rings. How to replace the piston rings in the engine yourself The thermal gap of the UAZ piston rings

You will need: keys "for 10", "for 12", "for 14", heads "for 15", "for 19", a hammer.

1. Remove the cylinder head (see "Replacing the cylinder head gasket").

2. Remove the engine oil sump and crankcase gasket (see "Oil sump seal replacement").

3. Remove the oil pump (see "Removal, repair and installation of the oil pump").

4. Turn away nuts of 1 rod bolts and remove a cover of 2 rods. If the lid is tight, knock it off with light blows from a hammer. Remove the insert from the cover.

5. Push the piston out of the cylinder and remove it along with the connecting rod. Remove the insert from the connecting rod.

6. Remove the remaining pistons with connecting rods.

7. Using a puller, remove the piston rings, in the absence of a puller, carefully straighten the rings at the locks.

10. Remove the remaining pistons from the connecting rods.

11. Wash all parts in gasoline. Clean the pistons from soot. Remove carbon deposits from the piston ring grooves with a piece of the old piston ring.

12. Inspect the pistons. If they have scuff marks, traces of burnout, replace the pistons. Measure the piston diameter. If it is less than 95.4 mm, replace the piston. The piston diameter is measured in a plane perpendicular to the axis of the piston pin, 8.0 mm below its axis. The piston is installed in the cylinder with a clearance of 0.036–0.060 mm. The pistons are divided by diameter into five size groups: A, B, C, D, D. The letter marking is stamped on the piston bottom. When selecting the piston to the cylinder, the clearance indicated above must be ensured. The maximum allowable clearance between the piston and the cylinder is 0.25 mm. The clearance between piston and cylinder can be determined by measuring the piston and cylinder. Spare parts are supplied with pistons of two repair sizes: with a diameter increased by 0.5 and 1.0 mm. On one of the bosses under the piston pin, the inscription is cast: “409” (piston of nominal diameter), “409AP” (diameter increased by 0.5 mm) or “409BR” (diameter increased by 1.0 mm).

13. Measure the clearance between the piston ring and the groove on the piston in several places around the circumference of the piston. The gap should be within 0.096–0.060 mm for compression rings and 0.115–0.365 mm for the oil scraper ring. If the clearances exceed the specified values, the rings or pistons must be replaced.

14. Measure backlashes in locks of piston rings. To do this, insert the ring into the cylinder and move the piston like a mandrel so that the ring fits in the cylinder evenly, without distortions. Measure the gap in the lock (in the socket) of the ring with a feeler gauge, it should be within 0.3–0.6 mm for compression rings and 0.5–1.0 mm for oil scraper discs. If the clearance is greater than specified, replace the ring. If the gap is smaller, you can file the ends of the ring with a file clamped in a vise. In this case, move the ring along the file up and down.

15. Check up landing of a piston pin in the top head of a rod. The clearance between the pin and the bushing of the upper head of the connecting rod should be within 0.0045–0.0095 mm. Pins, pistons and connecting rods are divided into four size groups and marked with paint. The finger is marked on the inner surface from one end, the connecting rod - on the rod, the piston - on the lower surface of one of the bosses or a Roman numeral is knocked out on the piston bottom. Dimensional groups of pistons, connecting rods and fingers are given in table. 5.3.

Lightly lubricate the piston pin with clean engine oil and insert into the upper end of the connecting rod. The finger should enter the head from the effort of the hand evenly, without jamming. The connecting rod must rotate on the piston pin under its own weight from a horizontal position. In the vertical position, the pin must not extend or fall out of the connecting rod head under its own weight. Piston pin and connecting rod must be the same or adjacent size groups.

Table 5.3 Dimensional groups of pistons, connecting rods and fingers of engines mod. ZMZ-409.10

16. Pistons with piston rings, pins and connecting rods assemblies are selected by weight. The difference in weight for one engine should be no more than 10 g.

17. Inspect the connecting rod bearings. If they have scuffs, chipping or other defects, replace the liners.

18. Establish on rods of a cover and measure diameter of an opening in the lower head of a rod. The nominal diameter of the hole is 60 + 0.019 mm, the maximum allowable is 60.03 mm. If the measured diameter exceeds the limit, replace the connecting rod with a cap. Measure the diameter of the hole in the connecting rod bushing. The nominal hole diameter is 22+0.007 -0.003 mm, the maximum allowable diameter is 22.01 mm. If the measured diameter exceeds the limit, replace the connecting rod. The dimensions of the connecting rod and piston group are given in Table. 5.4.

Table 5.4 Nominal and maximum allowable dimensions and fit of mating parts of the connecting rod and piston group of the engine mod. ZMZ-409.10

* The tolerance of 0.06 mm is divided into five groups (through 0.012 mm).

19. Assemble the piston 4 with the connecting rod 3. Preheat the piston to a temperature of 60–80 °C. Then quickly insert the connecting rod into the piston so that the inscription "Front" on the piston and the protrusion A on the connecting rod are on the same side, and press the piston pin 6 with a maximum interference of 0.0025 mm. Establish lock rings 5. Put on by means of a stripper piston rings on the piston.

Insert the insert 7 into the lower head of the connecting rod, while the locking protrusion (“lock”) on the insert should enter the recess in the lower head of the piston. Insert the insert 1 into the cover 2 of the connecting rod, while the fixing protrusion (“lock”) of the insert should enter the recess in the cover. Lubricate the cylinder, piston 4, crankshaft journal and bearings 1 and 7 with clean engine oil. Rotate the piston rings so that the compression ring locks are at 180° to each other, the oil scraper disc locks are at 180° to each other and 90° to the compression ring locks, the oil ring expander lock is at 45° to the lock one of the oil scraper discs. Turn the crankshaft so that the connecting rod journal of the cylinder in which the piston is installed is at bottom dead center (BDC). Insert the piston with connecting rod into the cylinder so that the inscription "Front" on the piston boss faces the front of the engine (camshaft drive).

Using a special mandrel, crimp the piston rings and lightly push the piston into the cylinder with a hammer handle, while the mandrel must be firmly pressed against the block, otherwise the piston rings can be broken. Move the piston down so that the lower head of the connecting rod sits on the connecting rod journal of the crankshaft, and remove the hose trimmings from the connecting rod bolts. Install the connecting rod cover 2 on the connecting rod bolts B on the connecting rod cap must be on the same side as the protrusion A on the lower head of the connecting rod, the cylinder numbers stamped on the connecting rod and the cover must be located on the same side, and the “locks” of the liners should be opposite each other.

20. Wrap the nuts of the connecting rod bolts and tighten to 68–75 N m (6.8–7.5 kgf m).

21. Install the remaining pistons with connecting rods in the same way.

22. Turn the crankshaft several times, it should rotate easily, without jamming.

23. Install the oil pump, oil sump and cylinder head.

1. Lay out the connecting rod and piston assemblies and sets of new rings so that in the process of measuring clearances and assembling the engine, the rings are constantly “tied” to their assemblies and cylinders.
2. Insert the top (No. 1) piston ring into the first cylinder of the engine and set it perpendicular to the cylinder walls, aligning by inserting the piston bottom first into the cylinder. The ring should be in the lower part of the cylinder, in the area of ​​\u200b\u200bthe boundary of the rings.

1. To measure the gap in the lock of the ring, insert the feeler blades into the space between the ends of the ring, picking them up so that their total thickness is equal to the gap. In this case, the probe should slide in the gap of the lock with slight resistance. Compare measurement results with requirements Specifications. If the gap exceeds the maximum allowable value, check again that the compared characteristic corresponds to the selected ring.

1. If the gap is too small, it must be increased to prevent the lock from closing during the thermal expansion of the ring during engine operation, as this can lead to serious consequences. The gap can be widened by carefully turning the ends of the ring in its lock with a file. Clamp the file in a vise with soft jaws, put the ring on the file with a lock and slowly pull it towards you, removing the material from the ends. Pull the ring towards you only (see picture below).

1. Excessive clearance in the lock of the ring is not a crime if it does not exceed 1 mm. Again, once again check the compared data for compliance with the checked ring. Make sure that the set of rings you purchase matches the type of engine in your car.
2. Repeat the procedure for each of the rings that will be installed in the first cylinder, then move on to the remaining cylinders. Remember to keep your rings in line with your pistons and cylinders.
3. After checking / adjusting the gaps in the piston ring locks, the rings must be installed on the pistons.
4. The oil scraper ring (bottom on the piston) is usually installed first. It consists of three separate sections. First, insert the ring expander into the groove on the piston. If a locking tab is used to prevent the ring from rotating, insert it into the hole in the groove. Then install the lower side section of the ring. Do not use a ring setting tool to fit the oil ring side sections onto the piston. Instead, insert one end of the section into the groove between the expander and the groove wall and, holding it firmly with your finger, gradually push the rest of the section into the groove, running the finger of the other hand with pressure along its perimeter. Then, in the same way, install the second side section of the ring.

1. After installing all three sections of the oil scraper ring, make sure that both (upper and lower) lateral sections of it rotate freely in the groove.
2. The middle (No. 2) compression ring is installed second. A mark is usually stamped on it, which should be facing upwards towards the piston crown during installation. The chamfered side of the second compression ring must face down on all engines, on 6-cylinder engines, the ring must be set with a two-point mark up, on V8 engines, the identification mark is a drill, a stamped letter O, an oval indentation, or the word TOR (up ).

1. Use a special tool to install the piston rings and make sure that the mark on the ring is facing up. Insert the ring into the middle groove on the piston. Do not spread the ring lock wider than it is really required to put it on the piston.

1. Install the top (#1) compression ring in the same manner. Make sure that the label (dot) is facing up. Do not confuse the top ring with the middle one. The first (top) compression ring must be installed with the chamfered side UP (whereas the second ring is fitted with the chamfered DOWN). Usually the second ring is marked from the top side two dots, and the first (upper) - one. Follow the instructions included with the kit.

1. Repeat the procedure for all remaining pistons.

Decreased vehicle performance can be due to many factors. Therefore, the "treatment" of such a disease must be selected correctly. A significant factor is the level of compression in the combustion chambers of the cylinder block. For such a diagnosis, the replacement of piston rings is suitable.

Additional signs will be the waste of engine oil and a decrease in fuel efficiency of the car. A more accurate picture will give a compression measurement using special instruments.

Consider an example of working on classic VAZ models. It is necessary to measure the compression on a warm engine. Cold engine readings can distort the picture. For measurements, you will need a special pressure gauge equipped with a threaded tip. You can buy it at any auto shop.

Appearance of the compressor

The test begins by unscrewing all the candles from their sockets. Then the central cable is disconnected from the ignition coil. We set the neutral gear and turn the throttle to the maximum opening. After that, we screw the compression gauge into one of the spark plug holes. At this time, the assistant should turn the starter handle. Two or three strokes will be enough.

Indications are considered normal if the data of 12-13 ks/cm 2 were set on the device.

Level 10 to 12 is also allowed. But if the numbers were below 10 kg / cm 2, then this indicates a low compression. If the compression still reaches a satisfactory level, but a little late, then in this case the responsibility may be on the valves.

To clarify, you can pour about 20 ml of oil into the controversial chamber and turn the starter again, making a measurement. When normal compression is set at 12 kg / cm 2, the reason lies in the rings. The correct installation of piston rings can solve it. If the pressure remains low, then the cause of the decrease is the valves.

Installation using a mandrel

Engine disassembly to replace rings

Before replacing, it is necessary to perform a number of preparatory work:

• it is necessary to drain the used engine oil, because after installing new rings, you need to fill in fresh working fluid;
• we loosen the exhaust pipe of the muffler;
• it is necessary to remove the cover of the valve mechanism and set the motor according to the marks;
• we dismantle the camshaft star, and for front-wheel drive VAZs we remove the bolt securing the belt pulley, and then the timing belt itself with the pulley;
• in the classics, we loosen the tensioner, and then we also dismantle the chain and star mounted on the camshaft;
• then we dismantle the rocker with springs, laying everything out in the correct order in order to assemble the parts in their places;
• remove the head of the block, before that you need to disconnect the manifold;
• unwind and get rid of the pan and oil pump;
• remove the connecting rod caps, and then push the connecting rods up so that you can pull them out along with the piston.

Checking rings and pistons

Each piston ring is removed and checked in its cylinder. In order not to confuse them with each other, it is necessary to immediately lay out the parts in a certain order. When checking old rings, their outer diameter should not create a gap with the cylinder walls by more than 1 mm. For comparison, you can insert a new ring into the same cylinder.

Checking the thermal gap in the rings

Measurements will usually be more accurate at the top of the block bore since volume wear is minimal.

The gap can also be checked in special gauges. It is necessary to pay attention to the thermal clearance in the piston rings, which should be in the range from 0.25 to 0.45 mm. It can be checked with a dipstick. If the parameter is less, then it is allowed to increase the gap by filing the end plane with a diamond file.

The diameter of the pistons is checked on the bottom (skirt). This is done with a micrometer.

It is necessary to compare this indicator with a table of acceptable values. Additionally, you need to check the clearance between the piston groove and the ring. In case of excess, the pistons must be changed. The tolerance limit is 0.15 mm. The pistons are also checked visually for cracks and the integrity of the ring bridges. After washing, satisfactory pistons can be used further.

Installation procedure

Branded products from trusted manufacturers have a convenient marking, thanks to which it is clear how to install piston rings correctly. On one side is written "TOP", which means "top" in English. This side should face towards the combustion chamber or the top of the piston.

Designation on the sides of the rings

If no inscription was found, then there should be a groove along the entire diameter. With such a step it is necessary to turn the ring down.

There are usually two installation methods. One of them is safer, and the second is more often used by either great professionals or absolute beginners. Both are suitable for independent use during repairs.

Mounting with metal plates

In the first case, you will need to cut several flat pieces of tin, about 0.3 to 0.5 mm thick. Three or four such sheets are arranged along the diameter of the piston. They wear rings. And they go down to the level of the slot. Then the mandrel for the piston rings is removed from the plates, and the ring sits in the desired groove. The method is perfect for any master.

Piston ring installation

The second option requires some experience and skill. It consists in the fact that you need to spread the gap with your fingers, increasing the inner diameter of the ring to the extent that you can pass the piston through it and install it in the desired groove. The disadvantages are that often inexperienced locksmiths break a lot of rings by applying more force than necessary.

Necessary actions after installing the rings

When each ring has taken its place in the groove, then you need to set the slots at about 120 degrees from each other. This reduces the likelihood of gas breakthrough from the fuel chamber into the crankcase cavity.

Incorrect installation of piston rings

There is evidence that the first ring holds about 75% of all compression, and the second - about 20%.

If the thermal gaps are separated, then when a certain amount of gas breaks through the first ring, it will not have time to get further, in contrast to the closer position of the second gap.

Errors when installing piston rings

Installing new rings in worn cylinders is absolutely inefficient. This is due to the fact that the worn hole has the shape of an ellipse. The expected quality lapping cannot occur.

Piston ring kit

Also, at high speeds, the second ring, consisting of cast iron, can simply burst.

During operation, the rings in the grooves fill the output. Such gaps depressurize the combustion chamber and gases from it enter the crankcase. And the oil goes in the opposite direction. Such a design can work out for several thousand kilometers, and then again it is necessary to carry out repairs.

It is also a gross mistake to deliberately set the gaps opposite each other. The gases overheat one side of the piston, resulting in a deformed part. There is a burnout of the metal and additional deformation of all elements.

And before assembly, it is necessary to assemble the pistons to the cylinders of the ZMZ-40906 engine. Pistons according to the outside diameter of the skirt and cylinders according to the inside diameter are sorted into five size groups. Pistons are marked with letters on the bottom. The letter of the designation of the size group of the cylinder diameter is applied with paint on the plugs on the left side of the cylinder block.

On the ZMZ-40906 engine, after repair, pistons with a nominal diameter of 95.5 mm and the first repair size of 96.0 mm (are marked "AP") can be installed. Pistons can be sorted into 2 weight groups. A group of heavier pistons is marked on the bottom. Pistons of the same mass group must be installed in the ZMZ-40906 engine. Pistons to cylinders must be matched group by group, in accordance with the table below.

* - Previously, the groups were designated by the letters of the Russian alphabet - "A", "B", "C", "G", "D", respectively.

It is allowed to select pistons for, including working cylinders without processing them, from neighboring groups when the piston passes the test below. It is recommended to check the suitability of the piston to work in the cylinder, as indicated below.

Checking the suitability of the piston for operation in the cylinder of the ZMZ-40906 engine.

1. The piston in an inverted position under the influence of its own mass or under the action of light pushes of the fingers of the hand should slowly lower along the cylinder.
2. Measure the pulling force with a dynamometer of a probe tape 0.05 mm thick and 10 mm wide, lowered to a depth of 35 mm between the cylinder wall and the piston inserted into it in an inverted position. The bottom edge of the piston skirt should be recessed 10 mm from the top end of the block.

Place the probe tape in a plane perpendicular to the axis of the piston pin, that is, along the largest diameter of the piston. The force when pulling the probe tape should be 29-39 N (3-4 kgf) for new cylinders and pistons. Measurements of cylinders, pistons and broaching of pistons should be carried out at a temperature of parts plus 20 + -3 degrees.

Selection of fingers for pistons and connecting rods and assembly of pistons with connecting rods and fingers.

Pistons are sorted into 2 size groups according to the diameter of the hole for the finger and are marked with a Roman numeral on the bottom. Connecting rods are sorted into 4 size groups according to the diameter of the pin hole and are marked with paint on the rod in the piston head area. Piston pins by outer diameter can be sorted into 5 size groups, which are marked with paint or Latin letters on the end, and into 2 size groups, which are marked with Roman numerals on the end.

Piston pins divided into 5 size groups and broken down into 2 size groups must be matched to the pistons and connecting rods separately in accordance with the tables below.

Connecting rods complete with a cover are sorted by weight into four groups and marked with paint on the connecting rod cover. Marking color:

- White - corresponds to the mass of the connecting rod 900-905 g.
– Green – 895-900
– Yellow – 890-895
– Blue – 885-890

For installation in the ZMZ-40906 engine, connecting rods of the same mass group should be taken. The difference in the mass of the units installed in the engine (piston with connecting rod) should not exceed 22 grams. Before assembly, lubricate the piston pin used on the engine and insert into the piston and connecting rod bores. Connecting rods and pistons, when assembled with a piston pin, must be oriented as follows: the inscription "FRONT" or "FRONT" on the piston, protrusion A on the crank head of the connecting rod must be directed in one direction.

Clean the piston crowns and piston ring grooves from carbon deposits. Use a feeler gauge to measure the backlash between the compression rings and the piston groove wall. For worn rings and pistons, a maximum clearance of not more than 0.15 mm is allowed. A larger clearance will result in increased oil burnout due to the "pumping" action of the rings. Replace, if necessary, worn ring or piston.

Fit the piston rings onto the piston using the tool. Install the lower compression ring with the inscription "TOP" (top) or the manufacturer's trademark marking towards the bottom (top) of the piston. The rings in the grooves must move freely.

Insert the pistons into the cylinders as follows.

– Orient the piston with the connecting rod so that the inscription "FRONT" or "FRONT" on the piston faces the front end of the cylinder block.
- Wipe the beds of the connecting rods and their covers with a napkin, wipe and insert the liners into them.
– Turn the shaft so that the cranks of the first and fourth cylinders are in the position corresponding to BDC.
– Coat bearings, piston, crankpin and first cylinder with clean engine oil.
- Separate the piston ring locks, shift the compression ring locks by 180 degrees relative to each other, set the locks of the annular disk elements of the oil scraper ring one to the other at an angle of 180 degrees and at an angle of 90 degrees to the compression ring locks. Set the lock of the spring expander at an angle of 45 degrees to the lock of one of the annular disk elements.
– Using a special mandrel with an internal conical surface, compress the rings and insert the piston into the cylinder.

Before installing the piston in the ZMZ-40906 engine block, you should once again check the correct position of the piston and connecting rod in the cylinder. Pull the connecting rod by the crank head to the connecting rod journal and put on the connecting rod cap. The connecting rod cover on the connecting rod must be installed so that ledge B on the connecting rod cover and protrusion A on the crank head or grooves for the liners are located on one side.

Tighten the nuts of the connecting rod bolts with a torque wrench to a torque of 68-75 Nm (6.8-7.5 kgcm). In the same order, insert the piston with the connecting rod of the fourth cylinder. Rotate the crankshaft 180 degrees and insert the pistons with the connecting rods of the second and third cylinders. Turn the crankshaft several times, which should rotate easily with little effort.

The fact that the car needs exactly the replacement of piston rings, and not some other repair work, will be told by the engine itself. Signs of such a malfunction appear quite clearly, so it will be difficult not to notice them. But before talking about the symptoms, you need to understand what the rings are and what role they play in the operation of the engine.

What are piston rings, their purpose

Piston rings are elastic open elements that are installed in special grooves on the piston housing. They are made of high-strength steel or cast iron, and coated with an alloying material on top. The alloy coating further increases the strength and also reduces the wear rate.

Usually 3 rings are inserted into the piston: 2 compression rings (occupy 2 upper grooves) and 1 oil scraper ring (lower groove). The task of the compression rings is to prevent the breakthrough of hot gases along the piston into the crankcase. Oil scraper - removes excess oil from the cylinder mirror, preventing it from entering the combustion chamber. In addition, the rings reduce the temperature of the piston by transferring almost half of its surface heat to the cylinder walls.

When the piston rings cease to cope with the tasks assigned to them, due to their wear, the car engine signals this by the manifestation of the corresponding symptoms.

Signs of worn piston rings

The fact that wear has reached a critical stage is indicated by blue or black. This indicates that excess oil entered the combustion chamber past the oil scraper ring and burned there along with the fuel. Black smoke coming out of the crankcase ventilation tube indicates that the compression rings, due to wear, allow gases to escape from the combustion chamber into its cavity.

Critical wear is accompanied by a decrease in compression (the ability to hold pressure) in the engine cylinders. This means that part of the gases formed during the combustion of the fuel mixture, which was supposed to push the piston, broke into the crankcase without doing useful work. This is what will lead to a pressure drop in the cylinder, therefore, the engine will lose some power. observed.

A special device - a compression gauge. When the pressure ratings are unknown (there is no instruction manual), it is first measured in a dry cylinder, then a little engine oil is poured through the candle hole, and the measurement is taken again. If the compression rises, then the rings need to be replaced. Similar signs can be observed in the case of their "occurrence".

"Occurrence" occurs when carbon deposits formed in the piston grooves prevent the piston rings from springing, resulting in a decrease in their tightness to the cylinder surface.

Such a problem, if the case is not very neglected, can be corrected with the help of special fuel additives. An engine that has a carburetor system can be tried with a carbon removal spray that is injected directly into the carburetor. If the removal of carbon deposits from the combustion chamber did not give an effect, then there is only one way out - replacing the piston rings and cleaning the grooves.

How to replace piston rings yourself

Of course, replacing rings is a rather laborious procedure. It requires accuracy and certain skills, but by and large there is nothing complicated in it (if you do not remove the engine). For this you need:

If the wear of the connecting rod bearings allows them to be reused, then it is not worth replacing, as this will require boring the crankshaft journals. It will not be possible to perform such work on your own without experience.

Tools required for work

To replace rings you will need:

• sets of open-end and box wrenches, as well as a wrench with an extension cord and heads with a nominal value of 10 - 19;
• torque wrench;
• specialist. crimp (mandrel).

In addition, you will need oil resistant. It will come in handy during the installation of the gaskets of the oil pan and valve cover.

And it seems that there is nothing complicated in the above actions if the replacement is made without removing the engine from the car. However, there are nuances, without taking into account which the engine with new rings will not work for a long time. When the cylinder reaches the limiting stage of wear, a "step" is formed on the surface of its mirror. Hitting it, the new ring will either break immediately or get a crack, which in the end will still lead to its breakage. In addition, the grooves of the old piston also have wear, so lapping new rings to the cylinder will be difficult or impossible at all. This means that it is better to entrust the troubleshooting of the piston group and cylinders to professionals.

Cylinder boring and honing should also be done by qualified personnel. In addition, this work can not be done without removing the engine. Therefore, before getting down to business, it is worth thinking carefully, realistically assessing your strengths and capabilities. So that the result of the repair would not be the replacement of the piston group as a whole, or even worse, you would not have to hand over the engine to.