Scheme for measuring cylinder diameter
A, B are the directions of measurements; 1, 2, 3 - belt numbers
Conrod bearing preload measurement for 1.4 l, 55 and 74 kW engines
a - outer diameter; b - diameter of the lower head of the connecting rod
Measuring the dowel pin protrusion of a 1.9L 74kW diesel engine
1 – a disk of the gauge of frequency of rotation of a cranked shaft; 2 - bolt; 3 - locating pin; a - protrusion of the pin
Details of the connecting rod and piston group are shown in the figures (see fig. Details of the connecting rod and piston group of the engine with a volume of 1.4 l, 55 and 74 kW, pic. Details of the connecting rod and piston group of engines 1.0 l, 37 kW and 1.4 l, 50 kW and fig. Details of the connecting rod and piston group of a diesel engine 1.9 l, 74 kW).
1. Clean the piston heads from carbon deposits. Clean the grooves for the piston rings, it is convenient to do this with a piece of the old piston ring.
2. Inspect the pistons: if they have scuff marks, traces of burnout, deep scratches, cracks, the pistons need to be replaced.
3. Measure backlashes in locks of piston rings. To do this, insert the ring into the cylinder in which it worked (for engines 1.0 l, 37 kW and 1.4 l, 50 kW from above, for other engines from below). Then push the ring with the piston, like a mandrel, into the cylinder so that it is installed in it without distortions at a distance of about 15 mm from the edge of the cylinder. Measure the gap in the ring lock with a feeler gauge, as shown in the figure. The values of the gaps are given in table. Piston ring gap.
4. If the measured clearance exceeds the limit, replace the ring. If the gap is less than the nominal, carefully grind off the ends of the ring with a needle file.
5. Check the clearances between the rings and grooves on the piston. To do this, insert the ring into the groove in which it stood, as shown in the figure, and measure the gap with a feeler gauge.
6. The nominal clearance for gasoline engines is 0.04–0.08 mm, the maximum allowable clearance is 0.15 mm (Clearances are for compression rings only), for diesel engines, the nominal clearance for the upper compression ring should be 0.06–0.09 mm, the lower one - 0.05–0.08 mm, the maximum allowable clearance for compression rings - 0.25 mm; for oil scraper rings, the nominal clearance is 0.03–0.06 mm, the maximum allowable clearance is 0.15 mm. If at least one of the gaps exceeds the maximum allowable, replace the piston with rings.
7. Examine the cylinders. If there are scratches, scuffs, shells, etc. on the cylinder mirror, bore the cylinders to the repair size (see table. Cylinder and piston dimensions) or replace the cylinder block, for engines 1.0 l, 37 kW and 1.4 l, 50 kW, replace the cylinder liners. With these defects with a depth of more than 0.5 mm, the unit cannot be repaired, it must be replaced.
8. Clear a deposit in the top part of cylinders. If a belt has formed there due to cylinder wear, remove it with a scraper.
9. Measure the cylinder diameters with a bore gauge. The cylinder diameter is measured in two perpendicular directions A and B (see fig. Scheme for measuring cylinder diameter) and three belts, while belt 2 passes through the middle of the cylinder, and belts 1 and 3 are 10 mm from the edge of the cylinder from above and below. If the measured diameter in at least one cylinder exceeds the nominal diameter by more than 0.08 mm for gasoline engines and by 0.1 mm for diesel engines, it is necessary to bore the cylinders to the next repair size or replace the cylinder block.
Attention! It is forbidden to measure the diameters of cylinders in a block fixed on an engine assembly stand by the power unit support bracket, as in this case the result may be erroneous.
10. Measure the piston diameter 10 mm from the bottom edge in a plane perpendicular to the piston pin as shown. If the obtained value differs from the nominal value by more than 0.04 mm, the piston must be replaced.
11. Inspect the liners of the main and connecting rod bearings: if they have cracks, scuffs, chips, chipping, etc., replace the liners. It is forbidden to carry out any adjustment work on the liners.
12. Inspect the crankshaft thrust half-rings: if they are found to have scuffs, risks, delaminations, the half-rings must be replaced. It is forbidden to carry out any fitting work on the half rings.
13. If there are deep risks, scratches, nicks, scuffs on the surfaces of the crankshaft on which the seals work, the crankshaft must be replaced.
14. If there are minor scuffs, risks, scratches on the main and connecting rod journals, you need to grind them to the nearest repair size. This work must be done at a service station. After that, polish the necks and blunt the sharp edges of the oil channels with an abrasive cone. Then wash the shaft and blow out the oil passages with compressed air. After grinding the necks, install the bushings of repair sizes. The dimensions of the necks of the crankshafts are given in table. Dimensions of crankshaft journals.
15. Measure the end clearance of the crankshaft. To do this, install the crankshaft with thrust washers and main bearing caps into the cylinder block. Tighten the cap bolts to 75 Nm for the 1.0l, 37kW and 1.4l, 50kW and 65Nm engines for the 1.9l, 74kW diesel engine. Fix the indicator so that its leg rests against the end of the crankshaft. Slide the crankshaft away from the indicator until it stops and set the indicator to zero, then slide the crankshaft in the opposite direction until it stops. The indicator will show the gap. If the gap exceeds the maximum allowable, it is necessary to replace the thrust half rings. The nominal axial clearance for engines 1.0 l, 37 kW and 1.4 l, 50 kW is: 0.03–0.13 mm, the maximum allowable is 0.26 mm; for a diesel engine 1.9 l, 74 kW, the nominal clearance is 0.07–0.17 mm, the maximum allowable clearance is 0.37 mm.
16. Check the clearances between the crankshaft journals and the main and connecting rod bearing shells. The clearances can be calculated by measuring the diameters of the crankshaft journals and the diameters of the main and connecting rod bearings, to which end, install the bearing caps with liners in place and tighten their fastening bolts to the appropriate torques. The manufacturer recommends measuring gaps with a plastic gauge wire as follows:
- thoroughly clean the bearings, crankshaft journals and liners from oil deposits;
- lay the crankshaft on the bed of the main bearings with the liners installed;
- put on the necks of the crankshaft trimmed calibrated plastic wire;
- install the bearing caps with the liners installed in them and tighten the bolts of their fastening to the appropriate torques. At the same time, do not turn the crankshaft;
- remove the bearing caps. The gap is determined by the degree of flattening of the wire using the scale on the wire packaging.
For a diesel engine of 1.9 l, 74 kW, the nominal clearance in the main bearings is 0.03–0.08 mm, the maximum permissible clearance is 0.17 mm, in the connecting rod bearings the maximum permissible clearance is 0.08 mm.
For engines of 1.4 l, 55 and 74 kW, the nominal clearance in the connecting rod bearings is 0.020–0.061 mm, the maximum allowable is 0.091 mm. If the gaps exceed the maximum allowable, it is necessary to grind the crankshaft to the next repair size.
17. Inspect the flywheel, if the teeth of its crown are damaged, replace the flywheel or its crown. To replace the crown, knock the old crown off the flywheel; to facilitate the operation, the crown can be heated. Then heat the new crown to 150°C, put it on the flywheel, if necessary hitting it evenly around the entire perimeter of the crown, push it all the way. If tint colors are visible on the contact surface of the clutch disc (flywheel was overheated), then the ring gear on the flywheel may have loosened. The defect is detected at the service station. A flywheel with a loose ring gear must be replaced.
18. Replace the connecting rods if they are bent or if there are burrs in the upper head. Connecting rods need to be replaced only assembled with caps, as they are machined together.
19. For 1.4 l, 55 and 74 kW engines, check the connecting rod bearing preload. To do this, measure in mm the outer diameter a (see fig. Conrod bearing preload measurement for 1.4 l, 55 and 74 kW engines) liner and diameter b of the lower head of the connecting rod, having previously installed its cover and tightened its fastening bolts to the appropriate torque. Then use the formula c = a - b to calculate the preload. The minimum allowable interference must be 1.5 mm. If the measured tightness is less than the minimum allowable, replace the liners.
20. For a diesel engine, check the protrusion of the dowel pin. To do this, on the crankshaft, unscrew the three bolts 2 (see fig. Measuring the dowel pin protrusion of a 1.9L 74kW diesel engine) fasteners and remove the disc 1. Measure the protrusion a of the pin above the end of the crankshaft, it should be 2.5–3.0 mm.
21. For 1.0L, 37kW and 1.4L, 50kW engines, check the protrusion of the cylinder liners above the top plane of the cylinder block as shown in the illustration. At the same time, the sleeve with a gasket 12 put on it (see fig. Details of the connecting rod and piston group of engines 1.0 l, 37 kW and 1.4 l, 50 kW) must be pressed firmly against the block. The protrusion should be 0.07–0.12 mm.
22. If the measured value is not within the specified limits, a new sleeve gasket must be selected. Spare parts are supplied with gaskets 0.10 thick; 0.12; and 0.14 mm. The difference in the values of the protrusion of the sleeves is allowed no more than 0.04 mm.
Piston ring gap
Piston ring | Engines | |||
1.0 l, 37 kW | 1.4 l, 50 kW | 1.4 l, 55 and 74 kW | Diesel 1.9 l, 74 kW | |
Nominal, mm: | ||||
- top compression | 0,2 – 0,5 | 0,4 – 0,72 | 0,2 – 0,5 | 0,2 – 0,4 |
- bottom compression | 0,2 – 0,5 | 0,3 – 0,62 | 0,4 – 0,7 | 0,2 – 0,4 |
– oil scraper | 0,4 – 1,4 | 0,4 – 1,4 | 0,4 – 1,4 | 0,25 – 0,5 |
Maximum allowable, mm: | ||||
- top compression | 1,0 | 1,0 | 1,0 | 1,0 |
- bottom compression | 1,0 | 1,0 | 1,0 | 1,0 |
– oil scraper | – | – | – | 1,0 |
Cylinder and piston dimensions
Diameter, mm | Engine 1.4 l, 55 and 74 kW | Diesel 1.9 l, 74 kW | ||
Piston | Cylinder | Piston | Cylinder | |
Nominal | 76,47 | 76,51 | 79,47 | 79,51 |
First repair | 76,72 | 76,76 | 79,72 | 79,76 |
Second repair | 76,97 | 77,01 | 79,97 | 80,01 |
Dimensions of crankshaft journals
Neck size | Engine 1.4 l, 55 and 74 kW | Diesel 1.9 l, 74 kW | ||||||||||||||||||
Main journal diameter, mm | Connecting rod diameter, mm | Main journal diameter, mm | Connecting rod diameter, mm | |||||||||||||||||
Nominal |
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First repair |
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Second repair |
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Third repair |
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