2. Measure the piston ring gaps in the grooves in height by installing the rings one by one in the corresponding grooves. The clearance between the ring surface and the piston groove surface is determined using a flat feeler gauge. If the ring gap exceeds 0.12 mm, then the rings or pistons are worn. The nominal value is 0.02–0.07 mm.
3. Insert all piston rings in order from the underside of the cylinder block into the cylinders. Using an inverted piston, the rings should be pressed down approx. 15 mm. In this case, both edges of the ring should be moved to measure the gap in the lock of the ring.
4. Nominal values are specified in Specifications. The wear limit is also different for different piston rings.
5. With too little clearance (for example, if the ring is new), the edges of the ring should be ground off, for this you need to clamp the file in a vise. If the gap in the ring lock is too large, the corresponding ring must be replaced.
6. Piston pins and connecting rod bushings should be checked for wear and wear. If at least one connecting rod is unusable, the entire set should be replaced.
7. The connecting rod bearing nuts must be replaced.
8. Connecting rods should be checked for bending and twisting in a special tool.
9. Check the connecting rod bolts for damage and replace if necessary. In this case, expansion bolts are used, and they should be replaced with the same ones.
Assembling the connecting rod and piston group
10. If the oil nozzle was removed to cool the piston, it must be screwed in together with the safety valve (27 Nm). The nozzles are located at the bottom of the cylinders.
11. If pistons are replaced, check that all pistons are of the same type.
12. Heat pistons to 60°C (put in hot water). Care should be taken to have a suitable tool that can be applied to the inside of the piston pin.
13. Press your fingers into the heated pistons and into the connecting rods.
14. When assembling pistons and connecting rods, the following requirement must be met:
- Arrow on the bottom of the piston (or painted or embossed on a new piston) must face the front of the engine.
- The cast lugs on the connecting rod and bearing cap must face the pulley.
- The cylinder number designations on the connecting rods and bearing caps must match.
15. Check that, after reassembly, the piston can swing freely on the connecting rod when moved in the direction of the arrow.
16. Using piston ring pliers, install the rings one by one into the grooves. Both compression rings can be mixed up, and therefore it is necessary to check their cross-section before installation. In addition, both compression rings are marked on one side with the word "Thor" or "Oben" and this designation after installing the ring should be read from above.
17. Install the three-piece oil scraper ring, distributing the locks evenly.
Installing the connecting rod and piston group
18. Lubricate the cylinders well.
19. Arrange all connecting rods according to cylinder numbers. The cast lugs on the connecting rods and bearing caps must face the crankshaft pulley.
20. The arrows on the bottom of the pistons must point towards the front of the engine.
21. Position the piston ring locks at equal distances around the circumference of the piston, i.e. through 120°.
22. Position the piston ring band as shown in the illustration and press the piston rings into the grooves. Check that they are well pressed in.
23. Slide short lengths of rubber or plastic tubing over the connecting rod studs to avoid scratching the cylinders.
24. Rotate the crankshaft until the two journals are in the BDC position.
25. Slide the connecting rod into the cylinder from above. For this, the engine must be laid on its side so that you can bring the connecting rods to the bearing journals and not scratch the cylinders or the connecting rod journals. The connecting rod bearing bush must already be in the connecting rod, with the protrusion in the recess.
26. Push the piston in until the rings slide one by one into the cylinder and the connecting rod base sits on the crankshaft journal. Do not scratch the bearing neck when doing this.
27. Place the second bearing shell into the cap, lubricate the shell well, slide the cap onto the connecting rod studs and tap lightly. Pieces of rubber tubes must first be removed. Be sure to pay attention to the fact that the cast protrusions on the connecting rod and the connecting rod bearing cap match, otherwise you can make a mistake at the last moment.
28. Lubricate the contact surfaces of the nuts on the connecting rod bearing caps with oil.
29. Tighten the nuts of the connecting rod bearing caps alternately to 30 Nm and tighten another 90°from this position, i.e. a quarter turn.
30. After tightening the connecting rod bearings, each bearing should be re-examined. From experience it is known that defects in connecting rod bearings sometimes appear after repairs are completed, when the bearing cap and connecting rod are not tightened perfectly. The number 1 in the illustration indicates both of the above-mentioned cast protrusions, and the number 2 indicates the designations of the connecting rod bearing cap and connecting rod, in this case for the second cylinder. The specified labels should be located on all connecting rods opposite each other. This check must be carried out before closing the engine crankcase.
31. After installing the connecting rods, the crankshaft must be rotated several times to determine if there are any jams. If there is, you need to check again if the pistons are in the correct position, i.e. the arrows on the bottoms must point forward (pulley side).
32. Using a feeler gauge, check the side clearance of the connecting rod to the crankshaft web. At the same time, push the connecting rod bearing to the right to measure the gap with a feeler gauge. This is the axial clearance of the connecting rod bearing and should not exceed 0.37mm. Install the oil pan.
The tightening torque of the mounting bolts is different for them.
33. From the front of the engine, loosen the crankshaft pulley bolts (vibration damper), while holding the flywheel.
34. On vehicles with automatic transmission unscrew the drive disk as described above.
35. Remove the cylinder head along with the intake manifold and exhaust manifold. Some parts are removed already when removing the engine (depending on its type).
36. Unscrew the pulley from the coolant pump and the lower toothed belt cover.
37. Mark the direction of rotation of the toothed belt with paint on the outside.
38. After loosening the belt tension nut, remove the toothed belt from the drive gears and tensioner. Camshaft (shafts) after that it can't be rotated.
39. Unscrew the oil pan.
40. Remove the oil pump.
41. If necessary, remove only the crankshaft, pistons and connecting rods can be left in the cylinder block. Otherwise, remove the pistons and connecting rods. If the pistons and connecting rods remain in the block, mark the connecting rod bearing caps in order, remove them and store with the bearing shells. Remember that damaged expansion bolts must always be replaced.
42. Install dial gauge (indicator) on a tripod to the front side of the cylinder block or fix it with a magnetic mount on the cylinder block by placing a feeler gauge against the crankshaft. Using a screwdriver, push the crankshaft to one side, set the dial gauge to zero, and push the crankshaft to the other side. The pointer gauge will show the axial clearance of the crankshaft and this value should be recorded. If it exceeds 0.25 mm, this must be taken into account during assembly. Inserts of average bearings are supplied with the adjusting half rings defining an axial backlash.
43. If a dial gauge is not available, the clearance can be measured on the middle bearing between the bearing flange and the crankshaft surface using a blade-type feeler gauge. To check with a dipstick (not more than 0.25 mm thick), the shaft must be pressed to one side.
44. Loosen the sealing flange mounting bolts on the front of the engine and remove the flange with gasket.
45. Remove the motor intermediate plate, remove the seal flange bolts and remove the seal flange. The intermediate plate is guided by guide bushings.
46. Loosen the crankshaft bearing cap bolts gradually in a criss-cross pattern and remove them in order. Check that the cap numbers are clearly visible. Cover No. 1 is located on the side of the pulley.
47. Remove the bearing shells and main journals and store them with their respective bearing caps. Keep in mind that some bearings have lubrication grooves while others do not.
48. Carefully remove crankshaft from crankcase.
49. Remove remaining liners from engine crankcase and store with other liners and bearing caps. These liners are provided with lubrication channels and must be reinstalled in the crankcase during assembly.
50. Remove the lower half rings on the middle bearing. They should be marked on the side.
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