Valvetrain Overview
Valvetrain Overview
• The cylinder head and guide frame must be replaced together.
• Do not start the engine for approximately 30 minutes after installing the camshafts. The hydraulic adjusting elements must seat themselves (otherwise the valves will seat themselves on 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 the gaskets and seals.
1 - Bolt
• Replace
• 50 Nm plus an additional 180° turn
2 - Camshaft Sprocket
3 - Seal
• Removing and installing, refer to => [ Exhaust Camshaft Seal ] Service and Repair
4 - Cylinder Head
5 - Valve Guide
• Checking, refer to => [ Valve Guides, Checking ] Testing and Inspection
6 - Valve Stem Seal
7 - Valve Spring
8 - Top Valve Spring Retainer
• Replace, refer to => [ Valve Stem Seals, Cylinder Head Installed ] Valve Stem Seals, Cylinder Head Installed or => [ Valve Stem Seals with Cylinder Head Removed ] Valve Stem Seals With Cylinder Head Removed
9 - Valve Retainers
10 - Hydraulic Valve Play Balancing Element
• Do not interchange
• Lubricate contact surface
11 - Fitted Key
• Make sure it is secure
12 - Exhaust Camshaft
• Check radial clearance using Plastigage (roller rocker lever removed)
• Radial play with bearing diameter 24 mm: 0.024 to 0.066 mm
• Radial play with bearing diameter 32 mm: 0.030 to 0.051 mm
• Run-out: max. 0.04 mm
13 - Guide Frame
• With integrated camshaft bearings
• Clean sealing surface, reworking is not permitted.
• Remove old sealant residue.
14 - Bolt
• Replace
15 - Camshaft Adjuster
16 - Bolt
• Replace
• 20 Nm plus an additional 45° turn
17 - Intake Camshaft
• Check radial clearance using Plastigage (roller rocker lever removed)
• Radial play with bearing diameter 24 mm: 0.024 to 0.066 mm
• Run-out: max. 0.04 mm
18 - Chain Tensioner
• Removing and installing, refer to => [ Camshaft Adjuster ] Camshaft Adjuster
• Before removing, secure with locking pin (T10115)
19 - Drive Chain
20 - Bolt
• 10 Nm
21 - Bolt
• 10 Nm
22 - Phase Sensor
23 - Exhaust Valve
• Do not reface, only lapping is permitted
• Valve guides, checking, refer to => [ Valve Guides, Checking ] Testing and Inspection
24 - Intake Valve
• Do not reface, only lapping is permitted
• Valve guides, checking, refer to => [ Valve Guides, Checking ] Testing and Inspection
25 - Cap
• Replace
• Removing: When guide frame is installed: Pierce through one side of the cover with an awl and pry it out
• Installing: Without sealant, press in 1 to 2 mm using the thrust piece (3334)
Cylinder Head Reworking Dimensions
- Resurfacing cylinder head (face grinding) is only permissible to minimum dimension a.
• Minimum dimension: a = 139.20 mm
Guide Frame Tightening Sequence
- Replace bolts
- Hand-tighten bolts in several stages - 1 to 6 - in sequence.
- Tighten the bolts in sequence - 1 to 6 - to 8 Nm using a torque wrench.
- Give 90° (1/4 turn) additional turn in sequence - 1 to 6 - using rigid wrench.
• Ensure guide frame is not tilted.
Valve Dimensions
• Intake and exhaust valves must not be refaced by grinding. Only lapping is permitted.
