Crankshaft Main Bearing: Service and Repair

11 21 531 - Replacing all main crankshaft bearing shells (M52/S52/M52TU/M54/M56)





Special tools required:
- 00 2 590 00 2 590 Plastigage (5)
- 00 9 120 00 9 120 Torque Angle Measuring Dial
- 11 2 110

(engine dismantled)





M52 B20/M52TU B20

M54 M22

Note:
Injection nozzles for cooling the pistons are installed in the bores of bearing seats 2 to 7.





M52 B25/B28

S52

M52TU B25/B28

M54 B25/B30

M56

Note:
Injection nozzles for cooling the pistons are installed on the underside of the cylinder between the bearing seats.

Installation Note:
Screw threads are coated with screw securing adhesive (Loctite).

Replace screws.





Important!
Observe grinding stage of crankshaft Crankshaft and Bearings M54.





Installation Note:
When replacing the bearing shells (also for replacement crankshaft), classification for bearing shell arrangement in engine block is waived.

Insert bearing shells with yellow color coding in engine block.





Note:
1. Install bearing shells with continuous lubricant groove and one retaining lug in engine block.
2. Fit bearing shells without continuous lubricant groove and two retaining lugs in bearing cover.





Note:
The axial guide on the crankshaft is fitted to bearing point 6.

Insert pilot bearing shell in the engine block.





Install crankshaft.

Note:
The crankshaft is marked with yellow, green or white paint according to the tolerance of the main journal.





Installation Note:
The bearing shell classification for the bearing cover is marked on the crankshaft in yellow, green or white paint.

Insert main bearing shells with same crankshaft color coding in main bearing caps.





The bearing shells are marked with yellow, green or white paint.

1. Bearing shell
2. Guide bearing
Observe grinding stage of main bearing journals Crankshaft and Bearings M54.





Note:
Bearing caps 1 to 5 are marked on exhaust side.

Bearing caps 6 and 7 are not designated.

Bearing cap 6 is a thrust bearing.





Check clearance on main crankshaft bearing.

Install crankshaft and place special tool 00 2 590 00 2 590 Plastigage (5) (Plastigage Type PG1) on oil-free crankshaft.

Do not twist crankshaft.





Install main bearing cap so that grooves in main bearing shell guide are one one side.

Align main bearing cap flush with side of bearing seat.





Installation Note:
To check main bearing clearance, use the old main bearing screws.

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





1. Tighten down main bearing screws with jointing torque.
2. Tighten down main bearing bolts with special tool 00 9 120 00 9 120 Torque Angle Measuring Dial to angle of rotation.
Tightening torque 11 11 1AZ 11 11 Engine Block.





Remove main bearing cap and read off bearing clearance at width of pinched plastic thread on measuring scale.

Radial crankshaft bearing clearance Crankshaft and Bearings M54.

If necessary, to correct bearing clearance, fit new bearing shells with a different color coding.





Remove plastic thread.

Coat main bearing shells and crankshaft with engine oil.

Install main bearing cap so that grooves in main bearing shell guide are one one side.

Align main bearing cap flush with side of bearing seat.





Installation Note:
Always replace bolts of main bearing cap with new bolts.

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





Note:
The reinforcement plates are not fitted on engines with gray cast iron engine blocks or on engines with oil pumps integrated in oil scrapers.

Installation Note:
Install reinforcement plates and fit screws with zero backlash.

Install main bearing shells and abut firmly.

Tighten down screw connection on reinforcement plates.





Tightening specifications for main bearing:

1. Tighten all screws on main bearing cover with jointing torque.
2. Unfasten screws on main bearing cover 6.
3. Strike back and front of crankshaft with plastic hammer to center thrust bearing (do not damage crankshaft).
4. Tighten screws of main bearing cover 6 with jointing torque.
5. Tighten down all screws of main bearing caps with special tool 11 2 110 or with special tool 00 9 120 00 9 120 Torque Angle Measuring Dial to torsion angle.
Tightening torque 11 11 1AZ 11 11 Engine Block.





Check axial play.

If permitted end float is exceeded, check crankshaft, guide bearing shells and engine block, replacing if necessary,

end float Crankshaft and Bearings M54.