To detect engine parts on a car, you will need: a portable lamp, a set of flat feeler gauges, a ruler, a caliper, a bore gauge, a micrometer, and a scraper.
1. Clean the piston head from carbon deposits. If the piston has scoring, burn marks, deep scratches, or cracks, replace the piston. Clean the piston ring grooves. It is convenient to do this with a piece of an old piston ring.
2. Clean the oil drain holes with a suitable piece of wire.
3. Check the gaps between the piston rings and the grooves on the piston.
Nominal clearance, mm:
- 0.04-0.075 - upper piston compression ring 1;
- 0.03-0.065 - lower piston compression ring 2;
- 0.02-0.055 - oil scraper ring 3.
The maximum permissible gap for all piston rings is 0.15 mm.
4. The most accurate way to determine piston ring clearances is by measuring the rings and grooves on the piston. To do this, use a micrometer to measure the thickness of the piston rings in several places around the circumference, then...
5. ... using a set of feeler gauges, measure the width of the grooves also in several places around the circumference. Calculate the average gap values (difference between piston ring thickness and groove width). If at least one of the gaps exceeds the maximum permissible value, replace the piston with rings.
6. Measure the gaps in the piston ring joints by inserting the piston ring into a special mandrel. If there is no mandrel, insert the piston ring into the cylinder in which it was used (or will it work if the ring is new), use the piston as a mandrel to push the ring into the cylinder so that it fits into the cylinder evenly, without distortions...
7. ...and measure the gap in the piston ring lock with a feeler gauge. The nominal piston ring clearance should be 0.25-0.45 mm, the maximum permissible (as a result of wear and tear) - 1.0 mm. If the piston ring gap exceeds the maximum allowable value, replace the piston ring.
8. If the piston ring gap is less than 0.25 mm, carefully file down the ends of the piston ring.
9. Check the clearances between the pistons and cylinders. The clearance is defined as the difference between the measured diameters of the piston and cylinder. The nominal clearance is 0.025-0.045 mm, the maximum allowable is 0.15 mm. If the clearance between the pistons and cylinders does not exceed 0.15 mm, pistons from the following classes can be selected so that the clearance is as close as possible to the nominal clearance. If the clearance between the pistons and cylinders exceeds 0.15 mm, bore the cylinders and install pistons of the appropriate repair size. Measure the piston diameter at a distance of 55 mm from the bottom in a plane perpendicular to the piston pin.
Figure 4.6. Cylinder measurement locations
10. Then measure the engine cylinder diameters in two perpendicular planes (figure 4.6) (B - along, A - across the cylinder block) and in four belts (1, 2, 3 and 4). For this you need a special device - a bore gauge.
11. When replacing parts of the connecting rod and piston group, it is necessary to select pistons for cylinders by class and one group by weight, as well as piston pins for pistons by class and connecting rods by weight. To select pistons for cylinders, calculate the gap between them. For ease of selection of pistons for cylinders, they are divided into five classes depending on diameters, each with 0.01 mm: A, B, C, D, E (Table 4.1).
Spare parts are supplied with pistons of nominal sizes of three classes: A, C, E and two repair sizes (1st repair size - increased by 0.4 mm, 2nd - by 0.8 mm).
According to weight, pistons are divided into three groups: normal, increased by 5 g and decreased by 5 g. Pistons of one group must be installed on the engine.
For pistons of repair sizes, rings of repair sizes increased by 0.4 and 0.8 mm are supplied as spare parts. The rings of the 1st repair size are stamped with the number "40", the 2nd - "80".
Table 4.1. Nominal dimensions of cylinders and pistons
| Mass of connecting rod heads, g | Marking | ||
| upper | lower | letter | with paint |
| 184±2 188±2 192±2 | 489±3 495±3 501±3 489+3 495±3 501±3 489±3 495±3 501±3 | F L B X M IN C N G | Red Green Blue |
12. Cylinder class designations are stamped on the lower plane of the block (mating surface under the oil pan) opposite each cylinder.
13. The following data is stamped on the piston bottom: 1 - piston class according to the pin hole; 2 - piston class by diameter; 3 - arrow showing the direction of piston installation; 4 - repair size (1st repair - triangle, 2nd repair - square); 5 - group by weight (normal - "G", increased by 5 g - "+", decreased by 5 g "-").
14. Replace cracked piston pins. The piston pin should easily enter the piston with the force of your thumb. Insert the piston pin into the piston. If play is felt when rocking the piston pin, replace the piston. When replacing a piston, select a piston pin according to its class (Table 4.2). Piston pins are divided by diameter into three classes (1, 2, 3) through 0.004 mm. The class of the piston pin is marked on its end with paint. The piston class according to the pin is stamped on the piston bottom, the connecting rod class according to the pin is stamped on the connecting rod cover.
15. Replace broken rings and oil scraper ring expander.
16. Replace broken or cracked piston pin retaining rings. The ends of the retaining rings must be in the same plane. Replace bent piston rings.
17. Replace bent connecting rods. Replace the connecting rod if there are burrs or deep scratches in the upper head bushing. Replace the connecting rod if, when disassembling the engine, it is found that the connecting rod bearings have turned in the connecting rod.
18. Insert the pin into the upper connecting rod head. If there is any play when you wiggle the pin, replace the connecting rod. Connecting rods assembled with caps are divided into classes according to the weight of the upper and lower heads (Table 4.3).
19. The engine must be equipped with connecting rods of the same class. The connecting rod marking is applied to its cover: 1 - connecting rod class by weight (letter or paint); 2 - class of connecting rod by pin.
Table 4.3. Connecting rod class by weight of heads and lower ends
| Mass of connecting rod heads, g | Marking | ||
| upper | lower | letter | with paint |
| 184±2 188±2 192±2 | 489±3 495±3 501±3 489+3 495±3 501±3 489±3 495±3 501±3 | F L B X M IN C N G | Red Green Blue |
20. If there are deep grooves, scratches, nicks on the surfaces on which the seals operate, the crankshaft must be replaced.
21. Measure the main and connecting rod journals of the crankshaft. Nominal diameters of crankshaft journals, mm:
- main necks - 50.799-50.819;
- connecting rod journals - 47.830-47.850.
If the wear or ovality of the crankshaft journals exceeds 0.03 mm, they must be ground to the nearest repair size.
There are four repair sizes with a reduction in the diameter of the crankshaft journals, mm:
- the first one - by 0.25;
- the second - by 0.5;
- third - 0.75;
- the fourth - by 1.00.
22. If there are minor burrs, scratches or notches on the main and connecting rod journals 1, they must be ground down to the nearest repair size. It is recommended that this work be carried out in a specialized auto repair shop. After grinding, polish the crankshaft journals and dull the sharp edges of the oil channel chamfers 2 with an abrasive cone. Wash the crankshaft and blow out the oil passages with compressed air. The ovality and taper of all crankshaft journals after grinding should not exceed 0.005 mm. After grinding the crankshaft journals, install the liners of repair sizes.
23. If there are burrs, scratches and delaminations on the working surfaces of the thrust half rings, replace the half rings. It is prohibited to carry out any adjustment work on the half rings.
24. Measure the crankshaft axial clearance. To do this, install the crankshaft and thrust half rings in the cylinder block and tighten the main bearing cap bolts (see "Engine assembly").
25. Install the indicator so that its leg rests against the crankshaft flange. Move the crankshaft away from the indicator until it stops and set the indicator arrow to zero. Move the crankshaft in the opposite direction. The indicator will show the size of the gap. The nominal axial clearance of the crankshaft is 0.06-0.26 mm, the maximum permissible is 0.35 mm. If the axial clearance of the crankshaft exceeds the maximum permissible, replace the thrust half rings.
The spare parts include two sizes of crankshaft thrust half rings: nominal size - 2.31-2.36 mm and repair size (increased by 0.127 mm) - 2.437-2.487 mm.
26. Inspect the connecting rod and main bearings. Replace connecting rod and main bearings with cracks, scoring, or chipping. It is prohibited to carry out any adjustment work on the connecting rod and main bearings.
Nominal thickness of connecting rod and main bearings, mm:
- main bearings - 1.824-1.831;
- connecting rod bearings - 1.723-1.730.
Connecting rod and main bearings are supplied as spare parts in four repair sizes, increased thickness, mm:
- the first one - by 0.25;
- the second one - by 0.50;
- third - 0.75;
- the fourth - by 1.00.
27. Check the clearances between the main bearing shells and the crankshaft journals. It is recommended that this work be carried out in a specialized auto repair shop. Measure the diameters of the journals and main bearings by installing the caps with liners on the block and tightening them to the appropriate torques. Calculate the gap. Clearances between the liners and the crankshaft journals:
- main bearings (nominal 0.026-0.073 mm, maximum permissible 0.15 mm);
- connecting rod bearings (nominal 0.02-0.07 mm, maximum permissible 0.1 mm).
If the clearance exceeds the maximum permissible value, the crankshaft must be ground to the next repair size.
28. In a specialized auto repair shop, you can measure the runout of the crankshaft journals.
The crankshaft journal runout should be:
- main journals and seating surface for the drive gear of the oil pump no more than 0.03 mm;
- landing surface for flywheel no more than 0.04 mm;
- the seating surface for pulleys and seals is no more than 0.05 mm.
29. Thoroughly clean and flush the crankshaft oil passages.
30. It is not recommended to press out the plugs yourself; for this purpose, contact a specialized auto repair shop.
31. Thoroughly clean the cylinder block surfaces from any remaining old sealing gaskets. Carefully inspect the cylinder block. If you find cracks, the cylinder block must be replaced as an assembly with the main bearing caps.
32. Check the tightness of the cylinder block cooling jacket. To do this, plug the hole for the water pump (installing the water pump with a gasket) and pour antifreeze into the cooling jacket. If a leak is visible anywhere, the unit is not sealed and needs to be replaced.
33. Inspect the cylinders. If there are scratches, burrs, cavities and other defects on the cylinder mirror, bore the cylinders to the repair size (it is recommended that this work be carried out in a specialized auto repair shop) or replace the cylinder block. If there are various defects deeper than 0.8 mm, the cylinder block cannot be repaired and must be replaced.
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34. Clean the carbon deposits from the top of the cylinders. If a belt has formed there due to wear of the cylinders, remove it with a scraper. Check the cylinder wear by measuring their diameters.
Table 4.2. Classes of piston pins, pistons and connecting rods
| Class | Diameter | Marking | ||
| fingers | hole in piston and connecting rod | fingers | piston and connecting rod | |
| 1 2 3 | 21,970-21,974 21,974-21,978 21,978-21,982 | 21,982-21,986 21,986-21,990 21,990-21,994 | Blue Green Red | 1 2 3 |