11 12 100 Removing and installing cylinder head (N20, 26)

Special tools required:

IMPORTANT: Fit new cylinder head bolts.
Do not wash off bolt coating.
Lightly oil washer on the contact surfaces (both sides).
There must be no coolant, water or engine oil in the blind holes.
Risk of cracking and corrosion!

Necessary preliminary tasks:

Remove EXHAUST SYSTEM .
Remove the catalytic converter . See 18 32 050 REMOVING AND INSTALLING/REPLACING CATALYTIC CONVERTER (N20) or 18 32 050 REMOVING AND INSTALLING/REPLACING CATALYTIC CONVERTER (N26) .
Remove exhaust turbocharger . See 11 65 020 REMOVING AND INSTALLING/REPLACING EXHAUST TURBOCHARGER (N20) or 11 65 020 REMOVING AND INSTALLING/REPLACING EXHAUST TURBOCHARGER (N26) with integrated exhaust manifold.
Drain COOLANT .
Drain ENGINE OIL .
Remove intake PLENUM .
Detach coolant hoses from cylinder head.
Remove CYLINDER HEAD COVER .
Remove INTAKE AND EXHAUST CAMSHAFT ADJUSTERS .
Remove INJECTOR SHAFTS .

IMPORTANT: Secure eccentric shaft (1) with open-end spanner (3) (risk of return stroke).

Slowly adjust eccentric shaft (1) to minimum lift via servomotor using 4-mm hexagon socket wrench (2) and open-end spanner (3).

Fig 1: Securing Eccentric Shaft

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Position eccentric shaft in the middle between maximum stroke and minimum stroke.

Secure eccentric shaft (1) with special tool 11 7 170 .

The open-end spanner can now be removed.

Fig 2: Checking Eccentric Shaft Movement

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Remove maximum stroke limit position (2).

Tightening torque: 11 37 5AZ .

Fig 3: Identifying Stroke Limit Position

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Unfasten engine wiring harness (1) at cylinder head cover.

Unscrew cable channel (2) from the cylinder head cover.

Unclip the cable channel (3) from the cylinder head cover.

Fig 4: Identifying Engine Wiring Harness And Cable Channel

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Unclip engine wiring harness (1).

Release screw (2).

Remove bracket (3).

Fig 5: Locating Bracket

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Release bolts (1) from timing chain module on cylinder head.

Tightening torque 11 31 4AZ .

Remove upper chain module upwards.

Fig 6: Identifying Timing Chain Module Bolts

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Remove VIBRATION DAMPER .

Open screw plug (2).

Fig 7: Identifying Screw Plug

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Tightening torque 11 11 7AZ .

Release right bearing journal (1) from chain module for timing chain on crankcase.

Tightening torque 11 31 5AZ .

Fig 8: Identifying Bearing Journal And Chain Module

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Press chain module slightly to one side.

Release screws (1).

Tightening torque 11 12 3AZ .

Fig 9: Identifying Screws Of Chain Module

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Release screw (1).

Tightening torque 11 12 3AZ .

Fig 10: Identifying Screw

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Various special tools are required for the cylinder head screw connection.

Screw M11 with special tool 11 8 580

Screw M9 with special tool 11 4 420 (old)

Screw M9 with special tool 2 318 428 (new)

Fig 11: Identifying Special Tool (11 8 580)

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Release cylinder head bolts in sequence 10 to 7 with special tool 11 4 420 .

Release cylinder head bolts in sequence 6 to 1 with special tool 11 8 580 .

NOTE: Graphics show intermediate lever, intake and exhaust camshaft.

Fig 12: Cylinder Head Bolts Tightening/Loosening Sequence (N20, N26)

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IMPORTANT: Removing and install cylinder head with a second person helping.

Weight of cylinder head with add-on parts is approx. 40 kg.

Do not rest cylinder head on sealing surface. Risk of damage to valves!

Remove coarse residues on sealing surfaces with special tool 11 4 471 from cylinder head and crankcase.

IMPORTANT: Do not use any metal-cutting tools.

Fig 13: Removing Coarse Residues On Sealing Surfaces

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Remove fine residues on sealing surfaces with special tool 11 4 472 from cylinder head and crankcase.

IMPORTANT: Do not use any metal-cutting tools.
There must be no coolant, water or engine oil in the pocket holes.
Risk of cracking and corrosion!

Clean all blind holes.

Replace CYLINDER HEAD GASKET .

Fig 14: Removing Fine Residues On Sealing Surfaces

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Fit new cylinder head bolts.

Insert cylinder head bolts (1 to 6) with special tool 11 8 580 .

Tightening torque 11 12 1AZ .

Insert cylinder head bolts (7 to 10) with special tool 11 4 420 .

Tightening torque 11 12 2AZ .

Fig 15: Cylinder Head Bolts Tightening/Loosening Sequence (N20, N26)

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Insert bolts (1).

Fig 16: Identifying Bolts Of Chain Module

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Tightening torque 11 12 3AZ .

Insert screw (1).

Tightening torque 11 12 3AZ .

Fig 17: Identifying Screw

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Assemble engine.