Timing Chain: Service and Repair

11 31 051 - Replacing timing chain (N51)

Special tools required:

Necessary preliminary tasks:
- Remove cylinder head cover Service and Repair.
- Remove all spark plugs.
- Remove chain tensioner Service and Repair.
- Remove radial shaft seal Service and Repair at front.
- Remove belt tensioner Service and Repair.
- Remove vibration damper Service and Repair.

Remove fastener (1) in direction of arrow.

Installation:
Install fastener (1) with bore facing outwards.

Secure crankshaft during entire repair operation with special tool 11 0 300.

Do not remove special tool 11 4 280.

Important!
Do not remove special tool 11 0 300 to release central bolt (1).
Employ a second person for gripping when releasing central bolt (1).

Mount special tool 11 9 280 on hub for vibration damper.

Release central bolt (1).
Tightening torque: 11 21 1AZ Mechanical Specifications.
Remove central bolt with hub towards front.

Open plug (1).
Tightening torque: 11 31 6AZ Mechanical Specifications.

Release screw (1) on chain drive at top.
Tightening torque: 11 31 2AZ Mechanical Specifications.

Release screw (1) on chain drive at bottom.
Tightening torque: 11 31 3AZ Mechanical Specifications.

Remove both adjusting units Removing and Installing/Replacing Inlet and Exhaust Adjustment Units.
Release screws (1).
Tightening torque: 11 31 2AZ Mechanical Specifications.
Remove timing chain module with timing chain and sprocket wheel upwards in direction of arrow.

Important!
Note installation direction of sprocket wheel (2).
Collar (see arrow) on sprocket wheel (2) points to crankshaft.
Incorrect assembly will result in engine damage.

Pull timing chain (1) upwards until sprocket wheel (2) engages chain guide (3).
Install timing chain (1) and sprocket wheel (2) in this position.

Installation:
Always keep timing chain tensioned; it is possible for timing chain (1) to jam on chain module (3).

Install hub with central bolt.
Tighten down special tool 11 5 200 11 5 200 Spacer Ring with screws (1).

Remove belt tensioner Service and Repair.
Screw in special tool 11 4 360.
Mount special tool 11 9 280 on 11 5 200.
Support special tool 11 9 280 on special tool 11 4 362.
Special tool 11 0 300 secures crankshaft.
Tighten central bolt (1) to jointing torque.
Tightening torque: 11 21 1AZ Mechanical Specifications.
Mark central bolt and hub with paint.

Apply stroke of paint (1) for torsion angle tightening to tool.
See illustration.

Important!
Do not remove tool from central bolt during torsion angle tightening - risk of damage.

Tighten central bolt with two persons.
Tightening torque: 11 21 1AZ Mechanical Specifications.
Install both adjusting units Removing and Installing/Replacing Inlet and Exhaust Adjustment Units.
Install chain tensioner Service and Repair.

Crank engine twice.
Check timing Adjustments.
Assemble engine.