Crankshaft Main Bearing: Service and Repair

11 21 531 Replacing All Crankshaft Main Bearing Shells (S63)

Special tools required:







IMPORTANT: Risk of injury from sharp edge of housing.







IMPORTANT:
If a crankcase or a crankshaft is replaced, old and new identifications can be used.
A mixed installation is permissible.

Example:
An old crankcase with an old crankcase designation and a new crankshaft with a new crankshaft designation.
An old crankshaft with an older crankshaft designation and a new crankcase with a new crankcase designation.
Or a new crankcase with a new crankshaft with new identifications.







Necessary preliminary tasks:
- Remove crankshaft







NOTE: Main bearing caps 1 to 5 are marked with punched numbers.







Observe crankshaft construction stage:

S: Series
B: Repair stage 1
C: Repair stage 2

The letters denote the bearing shell classification for the relevant bearing position from 1 to 5 (main bearing cap).
The first letter on the left applies to the first bearing position at the front on the timing chain drive.

Colour assignment on crankshaft 1 to 5
Y = yellow
G = green
V = violet







The letters denote the bearing shell classification for the relevant bearing position from 1 to 5 in the crankcase and is located on the transmission side in the Vee. The first letter on the left applies to the first bearing position at the front on the timing chain drive.

Colour assignment in crankcase 1 to 5.

Y = yellow
G = green
V = violet







IMPORTANT: New bearing shell classification.

The letters denote the bearing shell classification for the relevant bearing position from 1 to 5 (main bearing cap).
The first letter on the left applies to the first bearing position at the front on the timing chain drive.
Colour assignment on crankshaft 1 to 5







IMPORTANT:
Changed bearing classification:
Bearing position 1,2,3,4 and 5

Code letter Colour code
New (A to H) Yellow
Old Y Yellow
New (I to R) Green
Old G Green
New (S is Z) Violet
Old V












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.







NOTE: Main bearing cap number 3 can be identified by the surfaces (1) for the thrust washers of the thrust bearing.







Turn back thread support bushing into main bearing cap.







Checking main bearing clearance:
To check crankshaft bearing play, use the existing main bearing bolts.

IMPORTANT:
Risk of cracking.
No oil is permitted in the blind holes.

Do not twist crankshaft.
Place special tool 00 2 590 (Plastigage model PG 1) onto the oil-free crankshaft (see arrow).







Tighten down all collar bolts (M11) of main bearing caps in sequence 1 to 5 to jointing torque.
Tightening torque 11 11 1AZ.







Tighten down all collar bolts (M11) of main bearing caps with special tool 00 9 120 with angle of rotation.







Remove main bearing cap.
Read off main bearing clearance at width of flattened plastic thread with assistance of measurement scale.
Main bearing play.
- Remove plastic thread
- Apply a coat of oil to new bearing shells and crankshaft







NOTE:
Always replace main bearing bolts in main bearing caps with new bolts.
Do not wash off bolt coating.

IMPORTANT:
Risk of cracking.
No oil is permitted in the blind holes.

Install crankshaft.







Carefully strike back and front of crankshaft with a plastic hammer to centre guide bearing (do not damage crankshaft).
Secure special tool 11 6 252 with magnetic foot on crankcase.
Position special tool 11 6 251 .

Tightening specifications for main bearing:
Check axial play.
Check guide bearing shell, crankshaft and crankcase if necessary.







Assemble engine.