Removal
1. Remove the cylinder head.
2. Remove the valve springs and valve stem seals.
3. Remove the valves.
Examination
4. Wipe the valves and perform a visual inspection. Valves with burnt discs, insufficient valve disc height (b) or damaged and/or burnt stems must be replaced (figure 2.25).
5. Measure the alignment of the valve stems and valve seats. Replace the valve if necessary.
Figure 2.25. Valve dimensions and measurement of its runout.
Lapping
6. Grind the valve seats.
7. Measure the valve stem and valve seat runout again. If it is greater than the permissible value or the height h is insufficient, replace the valve. The valve dimensions are given in Table 2.1.
8. Measure the valve protrusion in the cylinder head.
9. Replace the valve and check for valve leaks.
Installation
10. Installation is carried out in the reverse order of removal.
Table 2.1. Valve dimensions
| Parameters | Engines 602.984/985 | ||
| Valve plate height h, mm | Exhaust valve, new | 1.75-2.05 | |
| Exhaust valve, permissible value | 1.6 | ||
| Inlet valve, new | 1.75-2.05 | ||
| Inlet valve, permissible value | 1.6 | ||
| Valve seat angle α,° | Exhaust valve | 45°15' | |
| Inlet valve | 45°15' | ||
| Valve seat width, mm | Exhaust valve | 2 | |
| Inlet valve | 2 | ||
| Alignment of valve seat and valve stem, mm | Exhaust valve | 0.03 | |
| Inlet valve | 0.03 | ||
| Protrusion of new valve (a) with new seat rings, mm | Exhaust valve Inlet valve | 0.1-0.7 0.1-0.7 | 0.1 0.5 0.1-0.5 |
| Distance from the end of the valve stem to the camshaft bearing T, mm | 20.4-21.4 | ||
(Original material on the website: «MERCEDESMAN.ru»)