Withdrawal
1. As described in the part A or B of this chapter, remove the cylinder head, flywheel, sump and baffle plate, oil pump and oil receiver.
2. Inspect the tops of the cylinders, possible protrusions from the development must be removed so as not to damage the piston during removal.
3. Using a set of flat feeler gauges, measure the backlash between the lower heads of the connecting rods and the crankshaft webs. Write down the received data for future use.
4. Rotate the crankshaft until the head and No. 1 piston are at BDC; piston number 4 will be installed later. If pistons and connecting rods are not numbered, mark them (for pistons, caps and connecting rods) with the help of a core (pic. 7.4). Note the orientation of the caps in relation to the connecting rods - at this stage, the manufacturer's marks can be difficult to see - draw arrows to correctly install when reassembling.
5. Turn away bolts/nuts of fastening of covers. Remove cover with insert (pic. 7.5, a, b). If the earbuds are to be reinstalled, tie them to your covers with tape.
6. If the covers are fastened with nuts, wrap the threaded part of the bolts with tape so as not to scratch the shaft journals during removal and installation (pic. 7.6).
7. Move the connecting rods up using the wooden handle of the hammer, and remove from the engine along with the pistons. Pay at At the same time, attention to the fact that the upper unworn belt of the cylinder, when removing the piston, can damage it or the rings. However, it is reasonable to note that with such wear, both pistons and rings will need to be replaced. If the piston and connecting rod are intact, tie the removed top bearing to them. On engines with oil-cooled piston nozzles, be careful not to damage them when removing the pistons.
8. Remove piston No. 4 in the same way and turn the crankshaft half a turn. Remove pistons #2 and #3. Before reassembly, keep the removed components grouped together for reassembly.
9. If necessary, unscrew the fastening screws and remove the oil nozzles at the bottom of the cylinders (pic. 7.9, a-c).
Examination
10. Use a screwdriver to remove the pin circlips from all pistons. Push out the pins and separate the pistons from the connecting rods (pic. 7.10, a, b). Vibrate retaining rings - new ones are required for installation. If the pin does not come out, heat the plunger to 60°C in hot water - this will facilitate removal.
11. Before checking the pistons, it is necessary to remove the piston rings using a puller or flat feeler gauges. Always remove the top compression ring first by stretching it over the piston crown. The rings are very brittle and can break if stretched too much - protect your hands from cuts from the sharp edges of the rings and your eyes from decaying fragments. After removing the rings, discard them - when repairing the engine, install new rings (pic. 7.11).
12. Remove carbon deposits from the piston grooves using old rings or their fragments (do not cut yourself with sharp edges of the rings). Remove only carbon deposits, do not remove metal and do not scratch the grooves. Protect your hands - wear gloves.
13. Scrape off any carbon deposits from the piston crown. A hand wire brush or a piece of sandpaper will help remove most of the carbon deposits.
Note: When cleaning pistons, keep their numbering and alignment markings.
14. After cleaning the pistons, wash the connecting rods with kerosene or other suitable solvent, dry them properly. Make sure that the oil passage holes in the piston grooves are not clogged with carbon deposits.
15. If the surface of the cylinder is not significantly damaged and the block does not require boring, you can install the old pistons. Normal piston wear shows up as vertical bald spots on the friction surfaces of the piston and a slight glorification in the fit of the top compression ring. When overhauling, new pistons should always be installed.
16. Carefully inspect the pistons - there should be no cracks in the bosses, skirt and piston baffles. Check the pistons for scoring on the rubbing surfaces, burnouts of the bottom and baffles. If the piston has scoring or shells, the engine may have overheated or the fuel combustion was incorrect, which caused especially high temperatures in the combustion chamber. In such cases, you need to check the cooling and lubrication systems. Burnouts on the piston skirt indicate that the rings did not seal the piston / cylinder gap. Burnouts of the piston bottom indicate a possible incorrect installation of the ignition, injection timing, detonation. If there are above problems, the cause must be corrected, otherwise the engine will fail again. These causes in gasoline engines can be caused by lean mixture due to air intake at the intake. In diesel engines, faulty injectors can be the culprit.
17. Check porosity, connecting rods, pins and connecting rod caps for cracks. Lay the connecting rods on a flat surface and, looking along the connecting rod, check for distortion. If there is any doubt about the working condition of the connecting rod, ask a suitably equipped workshop to weld it. Check the connecting rod bushing for wear and damage.
18. Using a micrometer, measure the diameters of the pistons at a point 10 mm above the skirt at right angles to the axis of the pin (pic. 6.18). Compare the obtained measurements with the data given in Specifications. If the piston dimensions are out of range, the pistons need to be replaced.
Note: If the cylinder block was reamed to the repair size during the previous repair, repair pistons must be installed. Record the measurements and use them to check piston/cylinder clearances when measuring cylinder bores, as described below.
19. Install a new piston ring in the corresponding groove and use a flat feeler gauge to measure the gap between the septum and the ring (pic. 7.19). pay attention to the fact that the rings are of different thickness - install the rings along the grooves. Compare the obtained measurements with the data given in Specifications. If the clearances are out of range, the pistons must be replaced. Confirm the result by measuring the thickness of the ring.
20. If there is wear or damage to the pin, the pin and connecting rod bushing can be replaced. It is better to entrust this work to specialists of a car repair shop.
21. When connecting the piston to the connecting rod, they must be oriented accordingly. An arrow is marked on the bottom of the piston (it may be contaminated) (pic. 7.21, a, b). When installing the piston in the block, the arrow must point forward of the engine. The connecting rod together with the cover have milled protrusions ("8" in fig. 7.21). Both lugs must face the engine (pic. 7.21). The piston with the connecting rod must be assembled in compliance with these requirements.
Pic. 7.21b. Piston components (1Z engine shown, others similar): 1. Piston rings; 2. Piston; 3. Finger; 4. Retaining ring; 6. Connecting rod bearing; 7. Upper surface of the cylinder block; 8. Krynka connecting rod bearing; 9. Guide bush (if there); 10. Oil nozzle for piston cooling; 11. Oil nozzle mounting screw; 12. Bolts for fastening the connecting rod bearing cap; A. Identification marks on the connecting rod and cap; B. Connecting rod and cap orientation marks
22. Lubricate the pin and bushing of the upper head with clean engine oil, insert the pin into the piston, aligning it with the upper head. Install new circlips on both sides of the pin. Repeat the procedure for the rest of the pistons.
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