Removal and Replacement
Valvetrain Assembly Overview
• Cylinder heads with cracks between the valve seats or between the valve seat and spark plug threads 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 the spark plug threads are cracked.
• After installing the camshafts, the engine may not be started for approximately 30 minutes. The hydraulic adjusting elements must seat themselves (otherwise the valves will seat themselves on the pistons).
• After working on the valvetrain, carefully rotate the engine by hand at least 2 full revolutions to ensure that the valves do not strike the pistons when starting.
• Always replace the seals and O-rings.
1 Double Bearing Cap
• Before installing, lightly apply sealant to the contact surfaces of front and rear bearing caps lightly. Refer to => [ Apply Sealant to the Bearing Cap ].
2 Bolt, 5 Nm + 90° (1/4) additional turn
• Always replace.
3 Hydraulic Valve Lifter
• Pressed into the roller rocker lever.
4 Exhaust Camshaft
• Checking axial play, refer to => [ Camshaft Axial Clearance, Checking ] Camshaft Axial Clearance, Checking.
• Removing and installing, refer to => [ Right Camshafts and Adjuster ] Right Camshafts and Adjuster.
• Check radial play using Plastigage (cam follower removed), wear limit 0.1 mm, run out Max. 0.01 mm.
5 Intake Camshaft Bearing Cap
• Note the installed position and allocation, refer to => [ Independent of the existing markings on the bearing caps, mark the sequence and install position on all bearing caps, as shown in the illustration. ] Left Camshafts and Adjuster.
• Observe the alignment bushings if present.
6 Exhaust Camshaft Bearing Cap
• Note the installed position and allocation, refer to => [ Independent of the existing markings on the bearing caps, mark the sequence and install position on all bearing caps, as shown in the illustration. ] Left Camshafts and Adjuster.
• Observe the alignment bushings if present.
7 Bolt, 5 Nm + 90° (1/4) additional turn
• Always replace.
8 Double Bearing Cap
9 Cap
• Always replace.
• To remove, push through using a screwdriver and pry out.
• To install, drive in using the retractor (3202) or a suitable lever.
10 Bearing Cap
• Before installing, lightly apply sealant to the contact surfaces of the front and rear bearing caps. Refer to => [ Apply Sealant to the Bearing Cap ].
11 Roller Rocker Lever
• For the exhaust camshaft.
• With the hydraulic valve lifter - item 3 -.
• Removing and installing, refer to => [ Roller Rocker Lever ] Removal and Replacement.
12 Drive Chain
• Installing:
• Left cylinder head, refer to => [ Place the drive chain onto the camshaft gears as follows: ] Left Camshafts and Adjuster.
• Right cylinder head, refer to => [ Place the drive chain onto the camshaft gears as follows: ] Right Camshafts and Adjuster.
13 Roller Rocker Lever
• For the intake camshaft.
• With hydraulic valve lifter - item 3 -.
• Removing and installing, refer to => [ Roller Rocker Lever ] Removal and Replacement.
14 Intake Camshaft
• Checking axial play, refer to => [ Camshaft Axial Clearance, Checking ] Camshaft Axial Clearance, Checking.
• Removing and installing, refer to => [ Right Camshafts and Adjuster ] Right Camshafts and Adjuster.
• Check radial play using Plastigage (cam follower removed) wear limit 0.1 mm, run out Max. 0.01 mm.
15 Bolt, 5 Nm + 90° (1/4) additional turn
• Always replace.
16 Camshaft Adjuster
• With the camshaft adjustment valve 1 (N205)
• Before removing, secure using the bracket for chain adjustment (3366). Refer to => [ Right Camshafts and Adjuster ] Right Camshafts and Adjuster.
17 Rubber/Metal Gasket
• Always replace.
18 Valve Retainers
19 Valve Spring Plate
20 Valve Spring
21 Valve Stem Seal
• Replacing, refer to => [ Valve Stem Seals ] Removal and Replacement.
22 Gasket
• Always replace.
23 Cylinder Head
• See note in => [ Valvetrain Assembly Overview ] Removal and Replacement.
• Checking valve guides, refer to => [ Valve Guides, Checking ] Testing and Inspection.
• Refacing valve seats, refer to => [ Valve Seat, Refacing ] Service and Repair.
24 Exhaust Valve
• Do not regrind, only lapping is permitted.
• Valve dimensions, refer to => [ Valve Dimensions ] [1][2]Specifications.
• Check valve guides, reface the valve seats, refer to => [ Valve Guides, Checking ] Testing and Inspection.
25 Intake Valve
• Do not regrind, only lapping is permitted.
• Valve dimensions, refer to => [ Valve Dimensions ] [1][2]Specifications.
• Check valve guides, reface the valve seats, refer to => [ Valve Guides, Checking ] Testing and Inspection.
26 Seal
• For the Camshaft Position (CMP) sensor.
• Replacing, refer to => [ Camshaft Position Sensor Seal ] Service and Repair.
27 Camshaft Position (CMP) Sensor Cover
• Note the installed position, notch in camshaft.
28 Washer
• Conical
29 Bolt, 23 Nm
30 Camshaft Position (CMP) Sensor
31 Bolt, 10 Nm
32 Roller Rocker Lever Shaft, Intake Side
• Removing and installing, refer to => [ Roller Rocker Lever ] Removal and Replacement.
33 Bolt, 10 Nm
34 Bolt, 10 Nm
35 Roller Rocker Lever Shaft, Exhaust Side
• Removing and installing, refer to => [ Roller Rocker Lever ] Removal and Replacement.
36 Bolt, 55 Nm
37 Camshaft Gear
38 Seal
• For the camshaft.
• Replacing, refer to => [ Camshaft Seals ] Removal and Replacement.
39 O-ring
• For the roller rocker lever shaft.
• Always replace
Apply Sealant to the Bearing Cap
- Lightly apply sealant to the hatched surface of the double bearing cap as well as the outer bearing cap next to the camshaft adjuster and install the bearing cap (observe alignment bushings).