You will need: tools needed to replace the head gasket (see «Replacing the cylinder head gasket») and for replacing valve stem seals (see «Replacement of valve stem seals»).
1. Disconnect the wire from the terminal «minus» battery.
2. Remove the cylinder head (see «Replacing the cylinder head gasket»).
3. Remove intake pipe (see «Replacing the intake pipe gasket»),
4. Remove the exhaust manifold (see «Exhaust manifold replacement»).
Helpful Hint: We recommend that you unscrew the spark plugs so as not to accidentally damage their insulators.
5. Clean the combustion chambers from carbon deposits. Examine the block head. If it has cracks or burn marks in the combustion chambers, replace the head Remove burrs and nicks on the surface of the block head.
6. Check up flatness of the surface adjoining to the block of cylinders. To do this, place a metal ruler with an edge on the surface of the head, first in the middle along, and then diagonally, and measure the gap between the plane of the head and the ruler with a feeler gauge. Replace the head if the gap exceeds 0.025 mm.
7. Remove camshafts (see «Removal, troubleshooting and installation of camshafts») and remove the hydraulic lifters from the sockets of the cylinder head.
Note: It is more convenient to remove the hydraulic compensator using a magnet or a suction cup. Hydraulic lifters cannot be interchanged, therefore, before removing them, they must be marked so that they can be installed in their original places during assembly. Store hydraulic lifters in the same position as they are installed on the cylinder head so that oil does not leak out of them.
8. Remove gasket residue and carbon from the surfaces of the flanges of the head for installing the intake pipe and exhaust manifold.
9. Check up presence of deformations of flanges for an inlet pipe and a final collector, replace the deformed head.
10. Repair damaged threaded holes by threading with taps or installing a repair sleeve (screw-in).
11. Check the tightness of the cooling jacket plugs. If their fit is weakened, restore it by chasing.
12. To check the tightness of the block head, plug the hole in the head under the thermostat socket. This can be done, for example, by installing a blank gasket made of thick cardboard under the thermostat housing and screwing in its fastening bolts.
13. Pour kerosene into the channels of the water jacket. If the level of kerosene drops during exposure for 15-20 minutes, then there are cracks in the head and it must be replaced. After checking, do not forget to remove the cardboard gasket.
14. Check up a condition of basic surfaces under necks of camshafts in a head of the block. If at least one of them shows signs of wear, scoring or deep risks, grind the bearing beds and measure the gap between the beds and the camshaft journals after grinding. If the gap is greater than the nominal, replace the block head.
15. To check the tightness of the valves, pour kerosene into the inlet and outlet channels of the head. If within 3 minutes kerosene does not leak from the channels into the combustion chambers, the valves are tight. Otherwise, rub (see «Lapping valves») or replace valves.
16. Place a suitable stop under the valve to be removed.
17. Install the valve spring compressor on the block head. After compressing the valve springs with the tool, remove the valve cotters. Then, gradually loosening the pressure on the tool handle, completely release the valve spring. Remove tool from block head...
18.... prying with a screwdriver, remove the valve spring plate...
19.... and remove the valve spring.
20. Remove the valve from the block head.
21. Install a special puller...
22.... and remove the valve stem seal.
Note: The valve stem seal is integral with the lower valve spring seat.
23. Similarly, remove the remaining valves and remove the valve stem seals.
24. Remove carbon from the valves and inspect them. Deformation of the valve stem and cracks on its plate are not allowed. Replace valve if damaged.
25. Check whether the working chamfer is too worn or damaged. Grinding of the working chamfer of valves is allowed (in repair shops with appropriate equipment). After grinding, the angle of the chamfer relative to the plane of the valve plate of the F16D engine should be from 45°to 45°25', the F18D engine - 44°. Minor scratches and scratches on the chamfer can be removed by lapping the valve against the seat (see «Lapping of valves»).
Warning: To avoid scratches on the valve stems, do not clean them with wire brushes or metal scrapers.
26. Check the concentricity of the valve disc and seat; apply a thin layer of graphite pencil lead to the chamfer of the valve head, insert the valve into the guide sleeve and, pressing lightly against the seat, turn.
27. Traces of graphite on the bevel of the seat indicate concentricity between the valve and seat.
28. Check up wear of a core of the valve in the places shown on fig. 5.9. The nominal diameter of the valve stem for the F16D engine is 6 mm, for the F18D engine it is 5.945-5.960 mm.
29. Check the condition of the grooves 3 of the valve stem for crackers. If there are traces of chipping of the edges of the grooves and wear of the cylindrical part, replace the valve.
30. Check the condition of the valve guides by measuring the inner bore diameter of the bushing and the diameter of the valve stem; the gap should not exceed 0.1 mm.
31. If the gap is greater than the allowable, repair the bushings by reaming to the repair size with an increase in the hole diameter by 0.075 mm relative to the nominal diameter. At the same time, it is necessary to install valves of the appropriate repair size in them with the provision of a nominal gap in the interface. Ream the bushing holes using a pilot shank reamer set. To avoid chipping of the bushing surface, the amount of metal to be removed on each pass and the tool feed should be kept to a minimum. Otherwise, replace the guide bushings. The nominal and repair dimensions of the guide bushings of the intake and exhaust valves are given in Table. 5.2.
32. Check the condition of the valve seats. Seat faces must be free of wear, pitting, corrosion, etc. The valve seats can be replaced by a specialist workshop. Minor damage (minor scratches, scratches, etc.) can be removed by lapping valves (see «Lapping of valves»).
33. More significant defects in the valve seats are eliminated by grinding, maintaining for the valve seats of the F16D engine dimensions 44.5-45°with a belt width after grinding for inlet valve seats 1.17-1.57 mm, for exhaust valve seats 1.14-1.8 mm; for valve seats of the F18D engine - 44°with a belt width after lapping for inlet valve seats 1.0-1.5 mm, for exhaust valve seats 1.7-2.2 mm. Saddles are recommended to be ground in a specialized workshop, as this requires special tools and equipment. If grinding does not give the desired result, replace the valve seats.
34. Replace valve stem seals regardless of their condition.
35. Inspect the valve springs. Cracks and reduction of elasticity of springs are not allowed. Twisted springs (deformation in a free state more than 1.6 mm) and replace cracked springs.
36. Always replace the gaskets of the intake pipe, exhaust manifold and cylinder head with new ones, since the gaskets that are removed, even outwardly not damaged, may be heavily compressed and will not ensure the tightness of the seals.