Crankshaft Main Bearing: Service and Repair

11 21 531 - Replacing crankshaft main bearing shells (N73)





Special tools required:
- 00 2 590 00 2 590 Plastigage (5)
- 00 9 120 00 9 120 Torque Angle Measuring Dial





Important!
Replace main bearing screws.

Do not wash off bolt coating.

There must be no oil in the blind holes (risk of cracking).





Necessary preliminary tasks:
- Remove engine Removing and Installing Engine.
- Remove left cylinder head Removing and Installing Left Cylinder Head (N73).
- Remove right cylinder head Removing and Installing Right Cylinder Head (N73).
- Remove hub Removing and Installing/Replacing Vibration Damper Hub (N73) for vibration damper.
- Remove lower timing case cover Removing and Installing Lower Timing Case Cover (N73).
- Remove rear timing case cover.
- Remove upper oil sump Removing and Installing/Replacing Oil Sump Top Section (N73).
- Remove oil pump Service and Repair.
- Remove flywheel Service and Repair.
- Remove all pistons Service and Repair.





Release taper screw mount (1) on all main bearing caps.

Release thread support bushings (2) on all main bearing caps.

Release main bearing bolts along lines (3).

Remove main bearing caps 1 to 7.





Main bearing shell (1) on bearing cap number 7 is a guide bearing.

Lift out crankshaft (2).





Unscrew thread support bushings in main bearing caps.





Installation Note:
Install main bearing shells (1) with lubrication groove in crankcase.

Install main bearing shells (2) without lubrication groove in the main bearing caps.





Bearing shell (1) with lubricating groove in crankcase

Installation Note:
The bearing shell classification for the relevant bearing position from 1 to 7 is stamped in the crankcase (2).

Y= yellow

G= green

V= violet





Checking main bearing clearance:

To check crankshaft bearing clearance, use old main bearing screws.

There must be no oil in the blind holes (risk of cracking).

Do not twist crankshaft.

Place special tool 00 2 590 00 2 590 Plastigage (5) (Plastigage model PG 1) on oil-free crankshaft.





1 - Tighten all screws on main bearing cover with jointing torque.
2. - Tighten down all screws on main bearing caps with special tool 00 9 120 00 9 120 Torque Angle Measuring Dial to torsion angle.

Installation Note:
Tightening torque 11 11 2AZ 11 11 Engine Block.





Remove main bearing cap.

Read off main bearing clearance with measuring scale.

Main bearing play.

- Remove plastic thread.
- Lubricate bearing shells and bearing shells.

Installation Note:
Always replace main bearing bolts.

Do not wash off bolt coating.

There must be no oil in the blind holes (risk of cracking).





Tightening specifications for main bearing:

1 - Tighten all bolts on main bearing cover to jointing torque.
2. - Release bolt on main bearing cap 7.
3. - Strike back and front of crankshaft with plastic hammer to center thrust bearing (do not damage crankshaft).



Check axial play.
4. - Tighten bolts of main bearing cap no. 7 to jointing torque.
5. - Tightening torque 11 11 2AZ.





Installation Note:
Replace main bearing bolts (3).

Tighten down all bolts of main bearings (3) with special tool 00 9 120 00 9 120 Torque Angle Measuring Dial.

Tightening torque 11 11 2AZ 11 11 Engine Block.

Installation Note:
Tighten down thread support bushing (2).

Tightening torque 11 11 3AZ 11 11 Engine Block.

Installation Note:
Replace flanged head screws (1) and tighten down.

Tightening torque 11 11 3AZ 11 11 Engine Block.





Install engine in reverse sequence to its removal.

Installation Note:
Replace all big-end bearings and main bearing shells.