5.11.2. Defektovka of engine details

It be required to you: portable lamp, set flat щупов, ruler, calliper, nutromer, micrometer, shaber.

After dismantling carefully wash up details kerosene, blow and dry them the compressed air (especially oil channels of details).

1. Examine the block, especially attentively support of a cranked shaft. Cracks in any places of the block are not allowed.

Good advice If there is a suspicion on existence of cracks in the block (hit of cooling liquid in a case or oils in cooling liquid), check tightness of the block at the special stand. Check carry out in the repair shops having the corresponding equipment.

2. Examine cylinders from both parties. Scratches, teases and cracks are not allowed.

Good advice At survey of cylinders we recommend to shine mirrors of cylinders with a portable lamp — so defects are visible much better.

Fig. 5.8. Scheme of measurement of cylinders: And – a belt of the greatest wear; B – a measurement zone after a rastachivaniye and a honingovaniye; In – a belt of the smallest wear

3. Determine by a nutromer the actual diameters of cylinders. Diameter of the cylinder measure in three belts (fig. 5.8). In each belt diameter measure in two mutually perpendicular directions (longitudinal and cross-section). In a zone over a belt A (at distance of 5 mm from the socket plane with a block head) cylinders practically do not wear out. On a difference of the sizes in this zone and in other belts it is possible to judge wear of cylinders. The nominal sizes of cylinders are specified in tab. 5.9. Ovality and a konusnost should not exceed 0,065 mm. If the maximum value of wear more than 0,15 mm or ovality exceeds the specified value, chisel cylinders till the closest repair size of pistons, having left an allowance of 0,03 mm for the diameter under a honingovaniye. Then отхонингуйте cylinders, maintaining such diameter that at installation of the chosen repair piston the settlement gap between it and the cylinder was 0,03 mm. To Defektovka, boring and a honingovaniye of the block carry out in the workshops having the special equipment.

4. Check a deviation from planeness of a surface of the socket of the block with a head of the block of cylinders. Put a calliper (or a ruler) to the plane:

– in the middle of the block;

– in the cross-section and longitudinal directions;

– on plane diagonals. In each situation flat shchupy define a gap between a calliper and the plane. It also will be a deviation from planeness. If the deviation exceeds 0,1 mm, replace the block.

5. Clear of a deposit the piston bottom a shaber (it is possible to make of an old file).

6. Clear of a flute deposit under piston rings an old ring, having inserted it into a flute the outer side and rolling on a flute.

7. Examine pistons, rods, covers: on them there should not be cracks.	8. Examine loose leaves: if on a working surface will find risks, teases and an otsloyeniye of an antifrictional layer, replace loose leaves new. All shatunny loose leaves are identical and interchangeable.

9. Measure diameter of pistons in the plane, a perpendicular axis of a piston finger, at distance of 19 mm from a skirt edge. Diameters of pistons of the nominal size are specified in tab. 5.10, diameters of repair pistons are increased by 0,29 and 0,50 mm. By results of measurements define a gap between the piston and the cylinder, if necessary pick up new pistons to cylinders. The settlement gap between the piston and the cylinder (for new details) makes 0,03 mm. It determine by a measurement of cylinders and pistons and provide with installation of pistons nominal or the repair sizes. The most admissible gap (at wear of details) – 0,15 mm. If at the engine which was in operation, the gap exceeds 0,15 mm, it is necessary to pick up pistons of the nominal size to cylinders or to establish pistons of the repair size with boring and a honingovaniye of cylinders: the gap should be most approached to the settlement.

10. Check flat shchupy a gap on height between flutes in the piston and rings, inserting a ring into the corresponding flute. The nominal (settlement) gap for both kompressionny rings makes 0,020 mm. If the ring is great on height and the gap is small, finish ring height to the necessary value, grinding it on an emery paper laid on a glass plate.	11. Check flat shchupy a gap in the lock of rings, having established a ring in the cylinder on depth about 50 mm.

Good advice To establish a ring without a distortion, advance a ring deep into the cylinder the piston. The gap should make 0,30–0,50 mm for both kompressionny rings and 0,40–1,40 mm for a maslosjemny ring. If a gap insufficient, cut butt surfaces of a ring. If the gap exceeds admissible, replace a ring.

12. All pistons of the nominal and repair sizes are made with a fine precision and do not demand preliminary sorting and selection for weight. If necessary it is possible to establish in separate cylinders the pistons which were in the use, if they in a good condition. Engine balancing in this case will not be broken.

13. Clear surfaces of piston fingers of varnish deposits, previously having softened them in solvent. Examine fingers. If on them cracks, excessive wear in a place of contact to lugs of the piston and traces from a provorachivaniye in the top head of a rod are found, replace fingers. Check interface of a piston finger and the piston, inserting previously the finger greased with engine oil into an opening of a lug of the piston. At ambient temperature of 20 °C the finger should enter into an opening by pressing of a thumb of a hand and not drop out of a lug in vertical position of the piston with a piston finger. It is necessary to replace a finger dropping out of a lug with another. If the finger again drops out, replace the piston with (tab. 5.11) finger.

14. Measure by a nutromer internal diameter of Dв of a seat of a rod assembled with a cover.

Note Before measurement tighten shatunny bolts the nominal moment.

15. Measure by a micrometer thickness of T of shatunny loose leaves.

Good advice In the absence of a special nozzle on a micrometer for measurement of a concave surface of the loose leaf it is possible to use a small ball. After measurement of the loose leaf it will be necessary to subtract diameter of a ball from the received size.

16. Measure by a micrometer diameter of Dн of shatunny necks.

17. Calculate z gap between shatunny loose leaves and necks of a cranked shaft on z formula = Dv-2T-Dn. The nominal settlement gap makes 0,011–0,058 mm. If the actual settlement gap less limiting, it is possible to use loose leaves which were established again. If a gap more limiting, replace loose leaves on these necks new (nominal thickness).

If necks of a cranked shaft are worn-out and перешлифованы till the repair size reduced by 0,25 mm, replace loose leaves repair (the increased thickness).

Necks grind besides existence of the general wear if on them is забоины and risks or ovality are made by more than 0,004 mm, and a konusnost — more than 0,005 mm.

18. Examine the top and bottom loose leaves of radical bearings. Loose leaves of the central (third) radical bearing differ from the others in bigger width. Besides, at their lateral end faces the wide fillets playing a role of basic half rings of the persistent bearing of a cranked shaft are executed. If on a working surface of loose leaves there were risks, teases, an otsloyeniye of an antifrictional layer, replace loose leaves new.

Prevention It is forbidden to perform any podgonochny operations on loose leaves.

19. Examine a cranked shaft. Cracks are not allowed. On the surfaces interfaced to working edges of epiploons, there should not be scratches, забоин, рисок. At detection them replace a shaft.

20. Measure by a micrometer external diameter of Dн of radical necks. The actual gap between loose leaves of radical bearings and radical necks of a cranked shaft determine by a technique stated for shatunny loose leaves. The nominal settlement gap makes 0,005 mm. If the actual settlement gap less limiting, it is possible to use loose leaves which were established again. If a gap more limiting, replace on these necks loose leaves new (nominal thickness).

If necks of a cranked shaft are worn-out and перешлифованы till the repair size with reduction of diameter by 0,25 mm, replace loose leaves repair (the increased thickness).

Necks grind besides wear existence if on them is забоины and risks or ovality are made by more than 0,004 mm, and a konusnost — more than 0,005 mm, reducing diameter by 0,25 mm (tab. 5.12).

21. Examine a bed of a cranked shaft. Cracks, scratches, faces and risks are not allowed. Establish to the place of a cover of radical bearings and measure by a nutromer internal diameter (see tab. 5.12).

22. Check parallelism of persistent fillets of an average radical neck: if they are not parallel, a cranked shaft will bend and should be replaced.