Valve train Overview

Valve train Overview

Risk of damaging valves and piston heads after working on valve train.

• The motor must not be started for about 30 minutes after installing camshafts because the hydraulic equalization elements must seat themselves.

• To ensure valves do not strike pistons when starting, carefully rotate engine at least 2 full revolutions.

• 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.

• The illustration shows the cylinder bank 2 cylinder head (left).






1 Sealing Plug

2 Valve Stem Seal

• Replacing with the cylinder head installed, refer to => [ Valve Stem Seals with Cylinder Head Installed, Replacing ] Valve Stem Seals with Cylinder Head Installed, Replacing

• Replacing with the cylinder head removed, refer to => [ Valve Stem Seals with Cylinder Head Removed, Replacing ] Valve Stem Seals with Cylinder Head Removed, Replacing

3 Valve Spring

• Installed location, refer to => [ Installed Position of Valve Spring ]

4 Hydraulic Adjusting Elements

• Clipped into roller rocker lever - 8 -

• Checking, refer to => [ Hydraulic Adjusting Elements, Checking ] Testing and Inspection

• Mark the installation position with paint for reinstallation

• Lubricate the running surfaces before installing

5 Valve Spring Plate

6 Valve Retainers

7 Securing Clip

• Not available individually

• Check for secure seat

8 Roller Rocker Lever

• Mark the installation position with paint for reinstallation

• Check roller for easy movement

• Lubricate the running surfaces before installing

• Clip to the hydraulic adjusting element - 4 - with the clip - 7 -

9 Intake Camshaft

• Removing and installing

• Measuring axial play, refer to => [ Camshaft, Measuring Axial Play ] Camshaft, Measuring Axial Play

• Radial clearance, measuring, refer to => [ Camshaft, Measuring Radial Play ] Camshaft, Measuring Radial Play

• Maximum run out: 0.04 mm

10 Gasket

• Replace

11 Bearing Bracket

• With integrated camshaft bearings

• Removing and installing, refer to => [ Camshafts ] Service and Repair

12 Bolt

• Tightening order, refer to => [ Camshaft Guide Frame Tightening Specifications and Sequence ]

13 Camshaft Position Sensor 2 (G163)

14 Bolt

15 O-ring

• Replace

16 Bolt

17 Camshaft Position Sensor 4 (G301)

18 O-ring

• Replace

19 Compression Ring

• For camshaft adjuster

20 Exhaust Camshaft

• Removing and installing, refer to => [ Camshafts ] Service and Repair

• Measuring axial play, refer to => [ Camshaft, Measuring Axial Play ] Camshaft, Measuring Axial Play

• Radial clearance, measuring, refer to => [ Camshaft, Measuring Radial Play ] Camshaft, Measuring Radial Play

• Maximum run out: 0.04 mm

21 Cylinder Head

• Check valve guides, refer to => [ Valve Guides, Checking ] Testing and Inspection

22 Intake Valve

• Do not reface, only lapping is permitted

• Mark the installed position for installation later

• Valve dimensions, refer to => [ Valve Dimensions ] [1][2]Specifications

• Check valve guides, refer to => [ Valve Guides, Checking ] Testing and Inspection

23 Exhaust Valve

• Do not reface, only lapping is permitted

• Mark the installed position for installation later

• Valve dimensions, refer to => [ Valve Dimensions ] [1][2]Specifications

• Check valve guides, refer to => [ Valve Guides, Checking ] Testing and Inspection

Camshaft Guide Frame Tightening Specifications and Sequence





• Replace bolts which have been tightened to an additional torque.

- Tighten the bolts in 3 steps according to the tightening sequence:






Installed Position of Valve Spring





• The tight spring coils - arrow - face toward the cylinder head.