You will need: keys "10", "12", "17", spark plug wrench, magnetized screwdriver (or tweezers) for removing valve spring crackers, device for compressing valve springs.
1. Remove all spark plugs (see "Replacement and maintenance of spark plugs").
2. Unscrew the three mounting nuts and remove the exhaust manifold heat shield.
3. Unscrew the remaining exhaust manifold mounting nuts and remove the manifold and the gasket installed underneath it (see "Replacing the exhaust manifold gasket").
4. Unscrew the four upper bolts securing the intake pipe to the cylinder head, unscrew the three lower nuts and remove the intake pipe together with the throttle assembly and fuel rail (see "Replacing the intake manifold seal"). Remove the intake manifold sealing gaskets.
Note: Replace the intake manifold gaskets with new ones each time the connection is disassembled.
5. Unscrew the three mounting bolts and remove the thermostat (see "Removing and installing the thermostat").
6. Remove the valve rocker shaft assembly with the rocker arms and the camshaft (see "Replacing the camshaft").
7. If necessary, remove the rocker arm clamps from the axle...
8. ...and valve rocker arms.
Note: If you do not plan to replace the valve rocker arms, their shaft and camshaft, do not remove the rocker arms from the shaft so that they can be installed in their original places during assembly.
9. Inspect the valve rocker arms. Replace the rocker arm if there is severe, clearly visible wear on the surface b that contacts the camshaft cam. Check the cleanliness of the hole b for supplying lubricant to the camshaft cam. Check the condition of the head of the adjusting bolt a and, if there are obvious signs of wear on it...
10. ...unscrew the bolt lock nut...
11. ...and unscrew the bolt from the rocker arm.
[The original can be found on the website: Renaultbook.ru]
12. Install the valve spring compressor, compress the springs, remove the crackers, spring plates, springs (see "Replacing valve stem seals") and remove the valves from the guide bushings.
Attention! After prolonged use, a mushroom-shaped burr may form on the upper end of the valve. Before removing the valve from the guide bushing, remove this burr with a file. It is strictly forbidden to knock the valve out of the guide bushing with a hammer through a mandrel without removing the burr, since this will inevitably damage the inner surface of the bushing.
13. Remove resinous deposits from the top surface of the head and from the intake ports. These deposits can be softened and washed off with kerosene or diesel fuel.
14. Clean the combustion chambers and exhaust channels from carbon deposits. Remove carbon deposits with a round metal brush installed in the chuck of an electric drill.
Note: Pre-soak carbon deposits with kerosene. Be careful: avoid inhaling dust generated during cleaning of combustion chambers. To prevent dust formation, periodically soak carbon deposits with kerosene.
15. Clean the inside surfaces of the valve guides with a thin cylindrical copper wire brush clamped in the chuck of an electric drill.
16. Remove any burnt-on remains of the sealing gasket from the mating surface of the head to the cylinder block.
Caution! Do not clean the mating surface of the head with metal brushes or emery cloth. Use a spatula made of hard wood or plastic, after softening the gasket residue with solvent.
17. After cleaning, inspect the cylinder head to prevent its operation with damaged threaded holes or cracks (especially between valve seats and in exhaust ports), corrosion, inclusions of foreign materials, cavities and fistulas.
Attention! It is forbidden to weld cracks, cavities and fistulas. Replace the defective head.
18. Using a metal ruler installed on its edge and a feeler gauge, check the flatness of the surface where the head meets the block in the longitudinal and transverse directions, as well as diagonally. If the gap between the edge of the ruler and the surface of the head exceeds 0.05 mm, replace the head.
19. Clean the surfaces of the head flanges for installing the intake pipe and exhaust manifold from gasket residues and carbon deposits.
20. Check for deformation of the flanges for the intake pipe and exhaust manifold; replace the deformed head.
21. Repair damaged threaded holes by tapping the threads or installing a repair sleeve (insert).
22. Determine the wear of the valve guide bushings by measuring the inner diameter of the bushing hole and the diameter of the valve stem, and by the difference in these dimensions, determine the clearance. The maximum allowable clearance for wear for intake valves is 0.10 mm, for exhaust valves - 0.15 mm.
23. If the clearance remains greater than the maximum permissible value even when installing new valves, replace the guide bushings. Replace the guide bushings in a specialized workshop with the appropriate tools and equipment.
24. Check the condition of the valve seats. There should be no signs of wear, cavities, corrosion or other defects on the working chamfers of the seats. The valve seats can be replaced in a specialized workshop. Minor damage (minor scratches, marks, etc.) can be removed by grinding the valves (see "Valve grinding").
25. More significant defects of valve seats are eliminated by grinding. Seats must be ground in a specialized workshop, as this requires special tools and equipment. If significant defects of the seats cannot be eliminated by grinding, replace the seats.
26. Remove carbon deposits from the valves and inspect them. Deformation of the valve stem 1 and cracks on its plate 2 are not allowed. If there is damage, replace the valve. Check whether the working chamfer 3 is too worn or damaged. Grinding the working chamfer of the valves is allowed (in repair shops with the appropriate equipment). After grinding, the thickness of the cylindrical part of the plate should be at least 0.5 mm for inlet valves and at least 1.0 mm for outlet valves. Minor scratches and marks on the chamfer can be removed by grinding the valve to the seat (see Fig. "Valve grinding").
Caution: To avoid scratches on the valve stems, do not clean them with wire brushes or metal scrapers.
27. Check the concentricity of the valve plate and seat: apply a thin layer of paint to the chamfer of the valve head (for example, Prussian blue), insert it into the guide bushing and, pressing it lightly against the seat, turn it. The traces of paint on the chamfer of the seat can be used to judge the concentricity of the valve and seat.
28. Check the condition of the grooves 4 (see photo p. 26) valve stem under the crackers. If traces of chipping of the groove edges and wear of the cylindrical part are found, replace the valve.
29. Replace the oil seals regardless of their condition.
30. Inspect the valve springs. Cracks and loss of elasticity of the springs are not allowed. Springs can be installed of one of two types. The nominal length of the first type of spring in a free state is (46.5±2) mm, the second type is (46.64±2) mm. The length with fully compressed coils is 26.0 and 23.63 mm, respectively. Springs whose length in a free state is less than the permissible value, curved (deviation of the spring axis from the vertical in a free state is more than 4°) and with cracks must be replaced.
31. Check the condition of the spring plates. Replace the plates with significant wear of the spring support grooves.
32. Install all removed parts and assemblies of the cylinder head in the reverse order of removal.
33. Always replace the cylinder head, intake manifold and exhaust manifold gaskets with new ones, since gaskets removed from the engine, even if they are not damaged externally, may be heavily compressed and will not provide a tight seal.