Replacing valve seat rings (Mercedes-Benz Vario 814)

1. Remove the valves.

2. Secure the cylinder head to the assembly table.

3. Check the inner diameter of the guide bushing using an indicator 4 (figure 3.13).

4. Remove valve seat rings 1 and 2 from cylinder head 3.

5. Measure the diameter of the valve seat ring bore (dimension B) in the cylinder head.

6. Ream the holes in the cylinder head for the valve seat rings.

7. Place the new rings in a box of liquid nitrogen and keep them there for about 20-30 minutes.

8. Heat the cylinder head in a water bath to a temperature of 80°C.

9. Using pliers, move rings 1 and 2 from the liquid nitrogen box into the holes in the cylinder head.

(Original published on the website Mercedesman.ru)

10. Install the rings using a punch. The rings must be installed without delay.

11. Machine the valve seat rings to the required dimensions (table 3.4).

12. Install the valves.

Table 3.4. Valve seat ring dimensions

Parameters		Engines 904
Outer diameter of inlet valve seat rings A, mm	Standard	35.07-35.08
	Rem. size 0.3	35.37-35.38
	Rem. size 0.5	35.57-35.58
Outer diameter of the exhaust valve seat ring A, mm	Standard	40.07-40.08
	Rem. size 0.3	40.37-40.38
	Rem. size 0.5	40.57-40.58
Height of valve seat ring E, mm	Inlet	7.6-7.7
	Outlet	8.0-8.1
Overlap of valve seat ring in cylinder head, mm	Inlet	0.045-0.080
	Outlet	0.045-0.080
Distance between the contact surface of the cylinder head and the outer surface of the valve seat ring D, mm	Inlet	3.7-4.0
	Outlet	3.3-3.6
Exhaust valve seat ring hole diameter in cylinder head B, mm	Standard	40.000-40.025
	Rem. size 0.3	40.300-40.325
	Rem. size 0.5	40.500-40.525
Depth of hole for valve seat ring in cylinder head C, mm	Inlet	11.4-11.6
	Outlet	11.4-11.6