5.15.2. Troubleshooting of details of the engine

After dismantling carefully clear, wash out and dry all details.
It will be required to you: portable lamp, set of flat probes, ruler, caliper, nutromer, micrometer, shaber.
1. Clear a piston head of a deposit. If on the piston there are teases, traces of a progar, deep scratches, cracks, replace the piston. Clean flutes under piston rings. It is convenient to do it by a fragment of an old ring.
2. Clean openings for an oil drain a suitable piece of a wire.
3. Check gaps between rings and flutes on the piston, previously having cleared rings of a deposit.
Nominal gap, mm:
0,04–0,075 – top compression ring 1;
0,03–0,065 – lower compression ring 2;
0,02–0,055 – oil scraper ring 3.
Maximum permissible gap for all rings of 0,15 mm.
4. Most precisely gaps can be determined by measurement of rings and flutes on the piston. For this purpose measure a micrometer thickness of rings in several places on a circle, then by means of a set of probes measure width of flutes also in several places on a circle. Calculate average values of gaps (a difference between thickness of a ring and width of a flute). If at least one of gaps exceeds maximum permissible, replace the piston with rings.
5. Measure gaps in locks of rings, having inserted a ring into a special mandrel. In the absence of a mandrel insert a ring into the cylinder in which it worked (or will work, if a ring new), advance the piston as a mandrel a ring in the cylinder that it was established in the cylinder exactly, without distortions and measure by the probe a gap in the ring lock. The nominal gap has to be 0,25–0,45 mm, maximum permissible (as a result of wear) – 1,0 mm. If the gap exceeds maximum permissible, replace a ring.
6. If the gap is less than 0,25 mm, accurately grind off a file ring end faces.

Fig. 5.14. Scheme of measurement of the cylinder

7. Measure diameters of the cylinder in two perpendicular planes (fig. 5.14) (In — lengthways, And — across the block of cylinders) and in four belts (1, 2, 3 and 4). The special device — a nutromer is for this purpose necessary. The nominal size of the cylinder (see tab. 5.1), ovality and conicity should not exceed 0,05 mm. If the maximum value of wear is more than 0,15 mm or ovality exceeds the specified value, chisel cylinders to the closest repair size of pistons, having left an allowance of 0,03 mm for diameter under a honingovaniye. Then an otkhoninguyta cylinders, maintaining such diameter that at installation of the piston the settlement gap between it and the cylinder was 0,025–0,045 mm. You carry out troubleshooting, boring and a honingovaniye of the block in the workshops having the special equipment.

Table 5.1 Nominal sizes of cylinders and pistons

8. Check a deviation from planeness of a surface of the socket of the block with a head of cylinders. Apply a caliper (or a ruler) to the plane:
– in the middle of the block;
– in the longitudinal and cross directions;
– on plane diagonals.
In each situation determine by the flat probe a gap between a ruler and плосколстью. It is also a deviation from planeness. If the deviation exceeds 0,1 mm, replace the block.
9. Check gaps between pistons and cylinders. The gap is defined as a difference between the measured diameters of the piston and cylinder. The nominal gap is equal to 0,025-0,045 mm, maximum permissible – 0,15 mm. If the gap does not exceed 0,15 mm, it is possible to pick up pistons from the subsequent classes that the gap was as it is possible closer to nominal. If the gap exceeds 0,15 mm, chisel cylinders and install pistons of the corresponding repair size. Measure diameter of the piston at distance of 10 mm from bottom edge of a skirt in the plane, perpendicular to a piston finger.
10. When replacing details of conrod and piston group it is necessary to pick up pistons to cylinders for a class and one group on weight, and also piston fingers to pistons on a class and rods on weight. For selection of pistons to cylinders calculate a gap between them. For convenience of selection of pistons to cylinders they are divided depending on diameters into five classes through 0,01 mm: A, B, C, D, E (tab. 5.1).
In spare parts deliver pistons of the nominal size of three classes: A, C, E and two repair sizes (the 1st repair size — increased by 0,4 mm, the 2nd — on 0,8 mm).
On weight pistons are broken into three groups: normal, increased by 5 g and reduced by 5 g. Pistons of one group have to be installed on the engine.
For pistons of the repair sizes in the spare part deliver rings of the repair sizes increased by 0,4 and 0,8 mm. On rings of the 1st repair size number "40", the 2nd – "80" is beaten out.
11. Designations of a class of cylinders are beaten out on the lower plane of the block (a privalochny surface under an oil case) opposite to each cylinder.
12. On the bottom of the piston the following data are beaten out: 1 – a piston class on diameter; 2 – the arrow showing the direction of installation of the piston; 3 – engine model.
13. Replace fingers with cracks. The finger has to enter easily the piston from effort of a thumb of a hand. Implant a finger into the piston. If when rocking a finger the side play is felt, replace the piston. When replacing the piston pick up to it a finger for a class.
14. Replace the broken rings and a dilator of an oil scraper ring.
15. Replace the broken or burst lock rings holding a piston finger. The ends of lock rings have to be in one plane. Replace the bent rings.
16. Replace the bent rods. Replace a rod if in the plug of 1 top head there are teases and deep scratches. Replace a rod if when dismantling the engine it is revealed that connecting rods were turned in a rod.

Prevention
Rods process together with covers therefore they cannot be razukomplektovyvat.

17. Implant a finger into the top head of a rod. If when rocking a finger the side play is felt, replace a rod. Rods assembled with covers on the mass of the top and lower heads are divided into classes.
18. Rods of one class have to be installed in the engine. Marking of a rod is put on the lower head and a cover of a rod.
19. If on surfaces on which epiploons work there are deep risks, scratches, zaboina, a bent shaft it is necessary to replace.
20. Measure radical and conrod necks of a bent shaft. Nominal diameters of necks of a bent shaft, mm:
– radical – 50,799–50,819;
– conrod – 47,830–47,850.
If wear or ovality of necks exceeds 0,03 mm, it is necessary to proshlifovat them to the next repair size.
There are four repair sizes with reduction of diameter of necks, mm:
– the first – 0,25;
– the second – 0,5;
– the third – 0,75;
– the fourth – 1,00.
21. If on radical and conrod necks 1 there are insignificant teases, risks, scratches, it is necessary to proshlifovat them to the next repair size. This work is recommended to be performed in a specialized workshop. After grinding polish necks and dull sharp edges of facets of oil channels 2 with an abrasive cone. Wash out a bent shaft and blow oil channels compressed air. Ovality and conicity of all necks after grinding should not exceed 0,005 mm. After grinding of necks establish inserts of the repair sizes.
22. If on working surfaces of persistent half rings there are teases, risks and peelings, replace half rings. On half rings it is forbidden to carry out any subracing works.
23. Measure an axial gap of a bent shaft. For this purpose install a bent shaft and persistent half rings in the block of cylinders and tighten bolts of fastening of covers of radical bearings (see. "Assembly of the engine").
24. Install the indicator so that his leg rested against a shaft flange. Shift a bent shaft from the indicator against the stop and establish an arrow of the indicator on zero. Shift a shaft in the opposite direction. The indicator will show gap size. A nominal axial gap of a bent shaft of 0,06-0,26 mm, maximum permissible – 0,35 mm. If the gap exceeds maximum permissible, replace persistent half rings.
In the spare part persistent half rings of two sizes are delivered: nominal – 2,31–2,36 mm and repair (increased by 0,127 mm) – 2,437–2,487 mm.
25. Examine connecting and radical rods. Replace inserts with cracks, teases, a vykrashivaniye. On inserts it is forbidden to carry out any subracing works.
Nominal thickness of inserts, mm:
– radical – 1,824–1,831;
– conrod – 1,723–1,730.
Inserts are delivered in spare parts of four repair sizes, the increased thickness, mm:
– the first — on 0,25;
– the second — on 0,50;
– the third — on 0,75;
– the fourth — on 1,00.
26. Check gaps between inserts of radical bearings and necks of a bent shaft. This work is recommended to be performed in a specialized workshop. Measure diameters of necks and radical bearings, having installed covers with inserts on the block and having tightened them with the replying moments. Calculate a gap. Gaps between inserts and necks of a bent shaft:
– radical bearings (nominal 0,026–0,073 mm, maximum permissible 0,15 mm);
– conrod bearings (nominal 0,02–0,07 mm, maximum permissible 0,1 mm).
If the gap exceeds a maximum permissible, bent shaft it is necessary to proshlifovat under the following repair size.

Prevention
When regrinding conrod and radical necks of a bent shaft on the repair size on the first cheek of a bent shaft it is necessary to put the corresponding brand, for example Sh 0,25 and K 0,25 respectively.

27. It is possible to measure a beating of necks of a bent shaft in a specialized workshop.
The beating has to make:
– radical necks and a landing surface under the leading gear wheel of the oil pump no more than 0,03 mm;
– a landing surface under a flywheel no more than 0,04 mm;
– a landing surface under pulleys and epiploons no more than 0,05 mm.
28. Carefully clean and wash out oil channels of a bent shaft.
29. It is not recommended to press off caps independently, for this purpose address in a specialized workshop.
30. Carefully clear the surfaces of the block of cylinders of the remains of old sealing laying. Attentively examine the block. If you find cracks, the block should be replaced assembled with covers of radical bearings.
31. Check tightness of a shirt of cooling of the block of cylinders. For this purpose muffle an opening under the water pump (having installed the pump with laying) and fill in antifreeze in a cooling shirt. If in some place the leak is noticeable, so the block is untight and it should be replaced.
32. Examine cylinders. If on a mirror of cylinders there are scratches, teases, sinks and other defects, chisel cylinders under the repair size (this work is recommended to be performed in a specialized workshop) or replace the block of cylinders. At various defects more than 0,8 mm in depth the block is not subject to repair and it should be replaced.
33. Clear a deposit in the top part of cylinders. If there the corbel owing to wear of cylinders was formed, remove it a shaber.
34. Check existence of nozzles for cooling of the bottom of the piston and durability of their landing in openings of beds of the block of cylinders.