Replacing the valve seat ring
1. Remove the valve springs.
2. Remove the valves.
3. Remove the glow plugs.
4. Remove the injector holder.
5. Remove the prechamber.
6. Measure the height of the cylinder head. If the obtained value is less than the permissible value, the cylinder head must be replaced.
7. Check the valve guides. Replace them if necessary.
8. Remove the valve seat ring using a ring puller.
9. Measure the main diameter D2 (figure 2.39a).
Figure 2.39a. Replacing the valve seat ring: A - Height (cylinder head height - separating surface - valve seat ring height); D - Outer diameter of valve seat ring; D1 - Inner diameter of valve seat ring; D2 - Main diameter of the hole for the ring; D3 - Seat chamfer diameter; H - Valve seat ring height; t - Depth of the hole for the valve seat ring; a-Saddle chamfer angle.
10. Cool the valve seat ring using liquid nitrogen and heat the cylinder head in a water bath to approximately 80°C.
11. Drive the valve seat ring into the valve seat hole using a punch. The valve seat ring must have full contact with the cylinder head. The dimensions of the valve seat ring are given in Table 2.5.
12. Grind the valve seats.
13. Installation is carried out in the reverse order of removal.
Table 2.5. Valve seat ring dimensions
| Parameters | Engines 602.984/985 | |
| Cylinder head height H, mm | New | 142.9-143.1 |
| Permissible wear after lapping (maximum removal approximately 0.5 mm) | 142.4-142.6 | |
| Inner diameter of guide bushing A, mm | Inlet valve | 8.000-8.030 |
| Exhaust valve | 9.000-9.050 | |
| Depth of hole for valve seat ring in cylinder head t for standard rings, mm | Inlet valve | 8.25-8.35 |
| Exhaust valve | 8.25-8.35 | |
| Radius R, mm | Inlet valve | 0.8 |
| Diameter D2 of standard ring, mm | Exhaust valve | 0.8 |
| Overlap of seat rings in cylinder head, mm | Inlet valve | 36.000-36.016 |
| Repair height of rings H, mm | Inlet valve | - |
| Exhaust valve | 36.500-36.516 | |
| Inlet valve | 0.068-0.100 | |
| Exhaust valve | 0.068-0.100 | |
| Inlet valve | 5.963-6.037 | |
| Exhaust valve | 5.963-6.037 | |
| Inlet valve | - | |
| Exhaust valve | 6.163-6.237 | |
| External diameter of standard ring D, mm | Inlet valve | 39.084-39,100 |
| External diameter of the replaced ring D, mm | Exhaust valve | 36.084-36.100 |
| Seat chamfer angle α, mm | Inlet valve | - |
| Chamfer diameter D3, mm | Exhaust valve | 36.584-36.600 |
| Inlet valve | 33.600-33.800 | |
| Exhaust valve | 30.400-30.600 | |
| Inlet valve,° | 45 | |
| Exhaust valve,° | 45 | |
| Inlet valve | 43.0-43.4 | |
| Inlet valve | 40.0-40.4 | |
Lapping valve seats
14. Measure the valve fit. If necessary, replace the valve seat ring.
15. Grind the valve seats (figure 2.396).
Figure 2.396. Lapping valve seats: (MB Sprinter Fig. 2B.1546): b - Saddle width; α - Valve seat angle; β - Upper correction angle; γ - Lower correction angle.
16. Replace the valves, check for valve leaks.
17. Check the valve fit. The dimensions of the valve seats are given in Table 2.6.
18. Install all removed components in the reverse order of removal.
Table 2.6. Valve seat dimensions
| Parameters | Engines 602.984/985 | |
| Valve seat width b, mm | Inlet valve | 1.2-1.7 |
| Valve seat angle α, | Exhaust valve | 1.5-2.0 |
| Valve seat ovality deviation,° | Inlet valve | 45°15' |
| Exhaust valve | 45°15' | |
| Inlet valve | 15°15' | |
| Exhaust valve | 15°15' | |
| Inlet valve, mm | 0.03 | |
| Exhaust valve, mm | 0.03 | |
| Fit of new valves to new valve seat rings, mm | Inlet valve | 0.1-0.5 |
| Exhaust valve | 0.1-0.5 | |
| Distance from the end of the valve stem to the main bearing of the camshaft T, mm | 20.4-21.4 | |