Valve Train, Servicing
Valve train, servicing
Note:
^ Cylinder heads with cracks between valve seats or between valve seat and spark plug thread can still be used without loss of service life if the cracks are minute (max. 0.3 mm width) or only the first four threads of a spark plug thread are cracked.
^ After installing camshafts, do not start engine for at least 30 minutes. The hydraulic valve lifters have to settle (otherwise valves will strike the pistons).
^ After working on the valvetrain, carefully rotate engine by hand at least 2 full revolutions to ensure that valves do not strike the pistons when starting.
^ Replace gaskets and O-rings.
^ Illustration depicts the left cylinder bank.
Part I
1. 10 Nm
2. Seals
^ Always replace
3. Housing
^ For camshaft adjustment valves
4. Gasket
^ Always replace
5. Exhaust camshaft
^ Check radial clearance using Plastigage (hydraulic valve lifters removed):
^ Wear limit: 0.1 mm
^ Max. run-out: 0.01 mm
6. Piston rings
^ For camshaft adjuster
^ Engage piston ring ends with each other go to Fig. 2
^ If ring ends are not of locking ring type (cannot be locked together) align all ring gaps at top and install camshaft housing using a gentle side to side motion (do not rock top to bottom)
7. Intake camshaft
^ Check radial clearance using Plastigage (hydraulic valve lifters removed):
^ Wear limit: 0.1 mm
^ Max. run-out: 0.01 mm
8. 10 Nm
^ Tighten in several stages from inside out
9. Guide frame
^ With integrated camshaft bearings
10. Sensor wheel
^ Note position (notch on camshaft)
11. 23 Nm
12. Hydraulic valve lifter
^ Do not interchange
^ Install with journal surface facing down
^ Before installing, check axial play of camshaft
^ Oil contact surface
13. Valve keepers
14. Valve spring retainer
15. Valve spring
16. Valve stem oil seal
^ Always replace
17. Camshaft Position (CMP) sensor
^ Cylinder bank 1 (right) Camshaft Position (CMP) sensor -G40-:
^ Cylinder bank 2 (left) Camshaft Position (CMP) sensor 2 -G163-
18. 10 Nm
19. Camshaft Position (CMP) sensor for exhaust camshaft
^ Cylinder bank 1 (right) Camshaft Position (CMP) sensor 3 -G300-
^ Cylinder bank 2 (left) Camshaft Position (CMP) sensor 4 -G301-
20. O-ring
^ Always replace
21. 10 Nm
22. Camshaft Position (CMP) sensor housing
23. Gasket
^ Always replace
24. Cylinder head
^ Observe note
^ Check valve guides, hand-lap valve seats
^ Reface valve seats
25. Intake valve
^ Do not reface, only hand-lapping is permitted
^ Mark installation position for reinstalling
^ Valve dimensions go to Fig. 1
^ Check valve guides, hand-lap valve seats
26. Exhaust valves
^ Do not reface, only hand-lapping is permitted
^ Mark installation position for reinstalling
^ Valve dimensions go to Fig. 1
^ Check valve guides, hand-lap valve seats
Part II
1. Seals
2. Housing
^ For camshaft adjustment valves
3. O-Rings
^ Green
^ Between solenoid valve housing and solenoid valves
^ Always replace
4. O-Rings
^ Black
^ Always replace
5. O-Rings
^ Green
^ Always replace
6. 4 Nm
7. Camshaft adjustment valve - intake side
^ Cylinder bank 1 (right) Valve -1- for camshaft adjustment -N205-
^ Cylinder bank 2 (left) Valve -2- for camshaft adjustment -N208-
^ Do not interchange with a valve for camshaft adjustment (exhaust side)
^ Note identification 12. 100 338
8. Gasket
^ Replace if damaged
9. Connector adapter
^ Must be replaced after disconnecting from camshaft adjustment valves
^ Carefully press onto harness connectors of camshaft adjustment valves until they engage
10. 4 Nm
11. Camshaft adjustment valve - exhaust side
^ Cylinder bank 1 (right) Camshaft Adjustment Valve 1 (exhaust) -N318-
^ Cylinder bank 2 (left) - Camshaft Adjustment Valve 2 (exhaust) -N319-
^ Do not interchange with a camshaft adjustment valve (intake side)
^ Note identification 12. 100 339
12. Gasket
^ Always replace
13. 10 Nm
Fig. 1 Valve dimensions
Note: Valves must not be refaced. Only hand-lapping is permitted.
WARNING:
^ Sodium-filled exhaust valves must not be scrapped without first being properly treated.
^ Using a metal saw, the valves must be cut in half between the shaft center and valve plate. They must not come into contact with water while being cut. After cutting open valves, throw not more than 10 at a time into a bucket of water. Then step back. A sudden chemical reaction will occur during which the sodium filling is consumed.
^ Valves that have been treated in this manner can then be disposed of as normal scrap metal.
Fig. 2 Engage piston ring ends, if necessary, or line up ring gaps at top
- Check whether piston rings at camshafts are installed and whether piston ring ends are engaged with each other.
Note: If ends of installed piston are not of the locking type (cannot be locked together):
^ Always orient the rings so that the gaps (of all three rings) are at the top of the camshaft prior to installation of the camshaft adjustment housing.
With all ring gaps aligned at the top of camshaft:
^ Install camshaft adjustment housing using a gentle side to side motion (do not rock top to bottom).
- If necessary, engage ends of installed piston rings (arrows), as depicted in illustration.