Valvetrain Overview

Valvetrain Overview

• The cylinder head and the cylinder head cover must be replaced together.

• After installing the camshafts, the engine may not be started for approximately 30 minutes. The hydraulic equalization elements must seat themselves (otherwise the valves will crash into the pistons).

• After working on the valvetrain and lifters, carefully rotate the crankshaft by hand at least 2 full revolutions before starting to be sure that valves do not strike the pistons.

• Always replace gaskets and seals.






1 Exhaust Valve

• Do not reface, only lapping is permitted

• Valve dimensions => [ Valve Dimensions ]

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

2 Cylinder Head

3 Valve Guide

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

4 Valve Stem Seal

• Replacing: cylinder head installed, refer to => [ Valve Stem Seals, Cylinder Head Installed ] Valve Stem Seals, Cylinder Head Installed, cylinder head removed, refer to => [ Valve Stem Seals with Cylinder Head Removed ] Valve Stem Seals With Cylinder Head Removed

5 Valve Spring

6 Valve Spring Plate

7 Valve Retainers

8 Hydraulic Adjusting Element

• Do not interchange

• Lubricate contact surface

9 Exhaust Camshaft

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

• Check radial clearance using plastigage (roller rocker lever removed)

• Radial play: 0.024 to 0.066 mm

• Run-out: maximum 0.04 mm

10 Cylinder Head Cover

• With integrated camshaft bearings

• Clean sealing surface, reworking is not permitted.

• Remove old sealant residue.

11 Bolt

• Replace

• Loosening => [ Loosening the Cylinder Head Cover ]

• Tightening order => [ Cylinder Head Cover Tightening Sequence ]

12 O-ring

• Replace

• Coat with engine oil

13 Camshaft Adjuster Actuator

14 Bolt

• 5 Nm

15 O-ring

• Replace

• Coat with engine oil

16 Sealing Plugs

17 Intake Camshaft

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

• Check radial clearance using plastigage (roller rocker lever removed)

• Radial play: 0.024 to 0.066 mm

• Run-out: maximum 0.04 mm

18 Cap

• Replace

• Removing: with the cylinder head cover installed, pierce through one side of the cover with an awl and pry it out

• Installing => [ Install the cap using the and without sealant. ] Camshafts

19 Intake Valve

• Do not reface, only lapping is permitted

• Valve dimensions => [ Valve Dimensions ]

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

Loosening the Cylinder Head Cover





- Loosen the cylinder head cover in a 1 to 6 sequence.

Cylinder Head Cover Tightening Sequence





- Replace bolts.

- Hand-tighten bolts in several stages in sequence - 1 to 6 -.

- Tighten the bolts in sequence - 1 to 6 - to 8 Nm using a torque wrench.

- Tighten the bolts an additional 90° using a rigid wrench in the sequence - 1 to 6 -.

• Make sure the cylinder head cover is not tilted.

Valve Dimensions





• Intake and exhaust valves must not be refaced by grinding. Only lapping is permitted.