Legendary Ulyanovsk plant
The Ulyanovsk Automobile Plant produced a lot of vehicles that have forever gone down in the history of the domestic automotive industry. "Loaves", patriots, "bobs" - most of the cars are designed for gas, ambulance, police, riot police, etc. UAZ Patriot is now popular as an all-wheel drive SUV that can overcome any obstacles. The plant released from under its wing a lot of minibuses, small trucks and cars with all-wheel drive.
The motors of these cars are distinguished by power, strength and reliability. The main reason for their breakdown is usually the great age of the UAZ. In the most common UAZ 3303 models, a 417 engine is installed. In order to repair the UAZ 417 engine with your own hands or overhaul it, you should not wait for the complete wear of all parts. The first signs of an imminent breakdown may be the following:
- greatly increased oil consumption;
- the motor smoked;
- significantly increased fuel consumption;
- engine power has dropped;
- the motor makes various suspicious sounds: knocks, squeaks and noises.
Each UAZ car has its own engine. For the UAZ 469 engine, a modification of the UMZ-451MI was first created, later upgraded to the UMZ 417 engine.
UAZ 3303 - cross-country vehicle. During overcoming various kinds of obstacles, the engine is overloaded most of all. It is easy to buy spare parts for this machine, both new and used.
Pistons and sleeves are destroyed due to frequent overheating of the engine when driving off-road. Many owners of the UAZ 3303 change the entire engine, and do not repair it. If the car owner undertakes to repair the engine with his own hands, he must understand that this requires some experience.
Do-it-yourself UAZ engine overhaul
Restoring the engine, returning it to its original agility and obedience will help change unusable parts or restore them. All parts must be of the correct size. The stores offer a varied selection of pistons, piston rings, intake and exhaust valve seats, crankshaft connecting rod bearing inserts. The size of the part can be checked with sales consultants.
Bulkhead UAZ engine
The wear of the engine is significantly affected by the deterioration of the lubrication of rubbing surfaces, which depends on the increase or decrease in clearances. To overhaul the motor with your own hands, you must first dismantle it. This is done in the following way:
- drain antifreeze and oil from the pan;
- separate the air intake filter and unhook the muffler pipe from the engine;
- disconnect the pipes of the cooling system, oil cooler and heaters from the engine;
- remove the radiator of the cooling system;
- separate from the carburetor the thrust of the throttle actuator and air;
- remove all wiring from the motor;
- unscrew the bolts of the lower and front cushions of the supports.
Now he removes the engine from the UAZ 3303. To do this, a bracket is installed on the studs of the head of the block, specially designed for this. The motor must be tightened with a jack and the gearbox separated from it. The motor can be removed by lifting it up.
Other actions will lead to the fact that, along with the engine, you will have to get the transfer case and gearbox.
What is important to consider when overhauling the UAZ 3303 engine
Before proceeding with the disassembly with your own hands, the motor should be carefully cleaned of fuel oil and slag. For dismantling, you will need special tool kits, such as 2216-B and 2216-M.
Required tool
All serviceable parts must be cleaned and put in place or marked with markers or stickers in order to avoid confusion in the future. In case of any breakdown or malfunction, the connecting rods and covers should not be separated from them. When changing the crankcase, you need to measure the angle of connection of the crankshaft axis with the rear end of the crankcase. Next, remove the clutch and determine the indicator stand on the edge of the crankshaft. The oscillation radius of the crankcase edge and slot should be approximately 0.1 mm.
After cleaning, all parts of the motor must be degreased. Carbon deposits can be carefully removed with a knife or other hard object. There is another, easier and safer way. To clean aluminum parts, you need to prepare the following solution:
- 10 g of laundry or other alkaline soap;
- 18 g of soda ash;
- 8 g of liquid glass;
- 1 liter of water heated to 90°C.
This solution is suitable for cleaning steel parts:
- 25 g of caustic soda;
- 30 g of soda ash;
- 5 g of laundry or other alkaline soap;
- 1.5 g of liquid glass;
- 1 liter of clean water at 90°C.
When the parts are clean, they must be rinsed in clean water and dried. When assembling the UAZ 3303 engine, certain rules should be followed:
- all parts subjected to friction during operation must be lubricated with engine oil;
- all new threaded parts must be installed on minium;
- use nitro-lacquer with one-piece parts;
- when tightening nuts and bolts, use a torque wrench.
Features of the repair of the cylinder block UAZ 3303
The cylinder block is the simplest component of the engine. Problems in its work arise due to the wear of the components. Therefore, you just need to replace the old worn parts with new or repaired ones.
Sleeves more often than other parts need to be replaced. A worn part can be considered when the gap between the skirt and the sleeve increases to 1/3 mm. The height of the protrusion of the sleeve in the cylinder block must be no more than 0.05 mm and not less than 0.005 mm. If the protrusion is too small, then the antifreeze will certainly be in the combustion chamber, which will result in a breakdown. The size of the sleeve is measured without taking into account the sealing ring. The liners in the cylinder block are fixed with washers and bushings. Excessively bored sleeves should be replaced with new ones.
The reason for the failure of the cylinder block may be the deformation of the surface adjoining the block, the complete abrasion of the valve guides and seats. The distortion of the head plane should not exceed 0.5 mm. Otherwise, the head needs to be polished.
piston mechanism
The condition of the piston rings should be monitored. It is better to change them every 80 thousand km of the rally. Each piston has 2 compression rings and 1 oil scraper. Thanks to the grooves on the inner surface of the ring, excess oil is removed from the system when the piston is raised up.
When only the rings need to be replaced, but not the piston itself, carbon deposits must be cleaned from the annular scars in its piston head. It is important to do this carefully to avoid damage to the side walls. With a 3 mm drill, you can remove carbon deposits from the oil outlet holes. The speed limit must not exceed 50 km/h during the first 1000 km.
When the top piston ring groove or piston skirt is worn, the piston itself should be replaced. New parts that will be installed in the cylinders must be of nominal size. The best option is when a new set of pistons is larger, this will eliminate the gap with an incompletely worn cylinder. The pistons are sorted by the outside diameter of the skirt. The size can be found on the bottom of the piston.
All parts of the connecting rod and piston group are divided into categories and are 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.
The finger lubricated with engine oil should move in the connecting rod head under the force of the thumb, but not fall out of the bushing.
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 piston replacement is not expected, check the groove width with 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 from the inside of the ring to the piston crown.
Install the top compression ring.
Dimensional groups of pins, pistons and connecting rods
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 the 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. Inspect the 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 " Front» on piston and lug « A” 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 fixing 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, crankshaft journal and bearings 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 ring 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 the 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 " Front” 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 « A» 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.
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).
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| 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 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.
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.
