All details connecting rod and piston group divided into categories and selected individually to each other.
The tolerance group, marked with a letter and stamped on the piston crown, ...
... must match the group indicated on the cylinder liner.
The values of the diameters of the holes in the piston bosses, the connecting rod head and the outer diameters of the piston pin are divided into groups and are indicated by paint.
On the piston pin, the group is indicated by paint applied on its end face or inner surface. It must match the group...
... indicated on the piston boss.
On the connecting rod, the group of holes for the piston pin is also indicated by paint. It must either match or be adjacent to the finger of the group.
We check the correctness of the selection of the connecting rod and piston pin in the following way.
Greased engine oil the finger should move in the connecting rod head under the force of the thumb, but not fall out of the sleeve.
On the side surface of the lower head of the connecting rod and the cover, the serial number of the cylinder in which it was installed is marked.
The numbers on the connecting rod cap and on the connecting rod itself must match and be on the same side.
The connecting rods supplied as spare parts do not have such markings, therefore, before disassembling them, mark the connecting rods and caps in the same way as the factory ones so as not to turn over and confuse the caps during assembly.
We heat the piston to a temperature of 60-80 ° C. It is allowed to heat the piston in hot water.
We introduce the connecting rod head between the piston bosses ...
... and with a hammer, through a mandrel or with a tool, we press in the piston pin lubricated with engine oil.
We fix the piston pin on both sides with retaining rings.
ATTENTION
The protrusion on the connecting rod cap must be on the same side as the inscription ...
ATTENTION
... "FRONT" on the piston.
The seats of the sleeves are thoroughly cleaned of scale and corrosion.
We replace the sealing copper washers of the cylinder liners with new ones.
We press the sleeves with light hammer blows through a wooden block.
With a set of probes, we check the protrusion of the sleeve above the plane of the block, which should be 0.02-0.10 mm.
We select piston rings for cylinders.
Alternately, we install the rings in the cylinder to a depth of 20-30 mm and measure the gaps with a feeler gauge. Compression rings should have a gap in the lock of 0.3-0.6 mm, oil scraper - 0.3-1.0 mm.
If the pistons are not to be replaced, we check the width of the grooves using new piston rings.
We check the clearance at several points along the circumference of the piston. The value of the side clearance for compression rings should be 0.050-0.082 mm, for the assembled oil scraper ring 0.135-0.335 mm.
In worn cylinders, you can install rings of the nearest repair size and, if necessary, file the ends to obtain a gap of 0.3 mm.
We put the rings on the piston, starting with the oil scraper ring.
Having opened the lock of the oil scraper ring expander, we install it in the lower groove of the ring, after which we bring the ends of the expander together.
We put an oil scraper ring on the expander ...
... the inscription to the bottom of the piston.
The angle between the locks of the expander and the ring is 45 degrees.
Installing the lower compression ring...
... inscription and chamfer with inside rings to the bottom of the piston.
Install the top compression ring.
Dimensional groups of pins, pistons and connecting rods
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. Install neutral gear and turn throttle valve maximum for 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. Can solve it correct installation piston rings. 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.
Examination thermal gap in 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. limit value tolerance 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 on high speed 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.
You will need: keys "for 10", "for 12", "for 14", heads "for 15", "for 19", a hammer.
Remove the cylinder head.
Remove the engine oil sump and crankcase gasket.
Remove oil pump.
Turn away nuts 1 rod bolts and remove a cover 2 rods.
If the lid is tight, knock it off with light blows from a hammer.
Remove the insert from the cover.
Push the piston out of the cylinder and remove it along with the connecting rod.
Remove the insert from the connecting rod.
If you are going to install the old liners, mark them with the cylinder number.
Remove the piston with the connecting rod from the cylinder carefully so as not to damage the cylinder mirror.
Check the marks on the connecting rod and its cap. If the marks are not visible, mark the connecting rod and cap with the cylinder number.
Remove the remaining pistons with connecting rods.
Remove the piston rings with a puller or, if it is not available, carefully straighten the rings at the locks.
Do not unbend the rings more than is required to remove them, otherwise the rings may become deformed or break.
8. Remove the circlips from both sides of the piston.
Press out the piston pins with a special tool.
If there is no tool, you can knock out the piston pins with light hammer blows through the mandrel 1. This must be done by weight so as not to damage the piston. Remove connecting rod 2 from piston 3.
Remove the remaining pistons from the connecting rods.
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.
Examine 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 piston pin axis, 8.0 mm below the piston pin 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 "409" (piston of nominal diameter), "409AP" (diameter increased by 0.5 mm) or "409BR" (diameter increased by 1.0 mm) is cast.
Measure the clearance between the piston ring and the groove on the piston at several places around the circumference of the piston.
The gap should be within 0.060–0.096 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.
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 (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 vice, moving the ring up and down along the file.
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.
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.
The piston pin and connecting rod must be of the same size group or adjacent groups.
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. Look around connecting rod bearings. If they have scuffs, chipping or other damage, 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 the table.
* Tolerance 0.06 mm divided into 5 groups (through 0.012 mm)
Assemble piston 4 with connecting rod 3. Pre-heat the piston to a temperature of 60-80°C.
Then quickly insert the connecting rod into the piston so that the inscription " Before» on piston and lug « BUT” on the connecting rod were on one side, and press in 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.
The upper compression ring is marked with the inscription “Top”, the ring must be installed on the piston with this inscription to the piston bottom.
A groove is made on the inner side of the lower compression ring, the ring must be installed with this groove upwards to the piston bottom.
Insert the bushing 7 into the lower head of the connecting rod - the locking protrusion ("lock") on the bushing should enter the recess in the lower head of the piston.
Insert the insert 1 into the cover 2 of the connecting rod - the fixing protrusion (“lock”) of the insert should enter the recess in the cover.
Lubricate the cylinder, piston 4, crankpin crankshaft and liners 1 and 7 with clean engine oil.
Orient the piston rings so that the compression ring locks are located at an angle of 180° to each other, the oil scraper disc locks are also at an angle of 180° to each other and at 90° to the compression ring locks, the oil scraper ring expander lock is at an angle of 45° to the lock of one of the oil scraper discs.
Turn crankshaft so that the connecting rod journal of the cylinder in which the piston is installed is at BDC.
Insert the piston with the connecting rod into the cylinder so that the inscription " Before” on the piston boss was facing the front of the engine (towards the camshaft drive).
In order not to damage the cylinder mirror, we recommend putting bushings made of soft material on the connecting rod bolts (for example, pieces of rubber or plastic hoses).
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 may be broken.
Move the piston down so that the lower head of the connecting rod sits on the connecting rod journal of the crankshaft, remove the hose trimmings from the connecting rod bolts.
Install the connecting rod cover 2 on the connecting rod bolts so that the ledge " B» on the connecting rod cap was on the same side as the protrusion « BUT» on the bottom head of the connecting rod; the cylinder numbers stamped on the connecting rod and cap were on one side, with the "locks" of the liners facing each other.
Wrap the nuts of the connecting rod bolts and tighten them to a torque of 68–75 Nm (6.8–7.5 kgf m).
Install the remaining pistons with connecting rods in the same way.
Turn the crankshaft several times, it should rotate easily, without jamming.
Install the oil pump, oil sump and cylinder head.
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 to, including to 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 divided 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 locks of the piston rings, shift the locks of the compression rings 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 locks of the compression rings. 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.
