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

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Special tools required:

NOTE: For special tools, refer to ENGINE - SPECIAL TOOLS .

00 2 590
00 9 120
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.

Fig 1: Identifying Injection Nozzles

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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:

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

Replace screws.

Fig 2: Replacing Screws

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IMPORTANT: Observe grinding stage of crankshaft.

Fig 3: Observing Grinding Stage Of Crankshaft

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Installation:

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.

Fig 4: Inserting Bearing Shells With Yellow Color Coding

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NOTE:

Install bearing shells with continuous lubricant one retaining lug in engine block.
Fit bearing shells without continuous lubricant two retaining lugs in bearing cover.

Fig 5: Installing Bearing Shells
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NOTE: The axial guide on the crankshaft is fitted to bearing point 6.

Insert pilot bearing shell in the engine block.

Fig 6: Inserting Pilot Bearing Shell

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Install crankshaft.

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

Fig 7: Crankshaft Is Marked With Yellow, Green Or White Paint According To Tolerance Of The Main Journal

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Installation:

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.

Fig 8: Inserting Main Bearing Shells

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

Bearing shell
Guide bearing

Observe Grinding Stage Of Main Bearing Journals.

Fig 9: Observing Grinding Stage Of Main Bearing Journals

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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.

Fig 10: Identifying Bearing Caps

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Check Clearance On Main Crankshaft Bearing.

Fig 11: Checking Clearance On Main Crankshaft Bearing

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Install Crankshaft And Place Special Tool 00 2 590 (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 side.

Align main bearing cap flush with side of bearing seat.

Fig 12: Identifying Main Bearing Cap Grooves

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Installation:

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

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

Tighten down main bearing screws with jointing torque.
Tighten down main bearing bolts with special tool 00 9 120 to angle of rotation.

Tightening torque, refer to 11 11 1AZ in ENGINE - TIGHTENING TORQUES .

Fig 13: Tightening Down Main Bearing Bolts With Special Tool 00 9 120

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

Fig 14: Removing Main Bearing Cap

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Radial crankshaft bearing clearance; 0.020... 0.058 mm.

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 side.

Align main bearing cap flush with side of bearing seat.

Fig 15: Installing Main Bearing Cap

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Installation:

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.

Fig 16: Tightening Down Screw Connection

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Installation:

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:

Tighten All Screws On Main Bearing Cover With Jointing Torque.
Unfasten Screws On Main Bearing Cover 6.
Strike Back And Front Of Crankshaft With Plastic Center Thrust Bearing (Do Not Damage Crankshaft
Tighten Screws Of Main Bearing Cover 6 With Jointing Torque.
Tighten Down All Screws Of Main Bearing Caps With Special Tool 112110 Or With Special Tool 00 9 120 To Torsion Angle.

Fig 17: Tightening Down All Screws Of Main Bearing Caps With Special Tool 112110 Or With Special Tool 00 9 120
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Tightening torque, refer to 11 11 1AZ in ENGINE - TIGHTENING TORQUES .

Check axial play.

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

Fig 18: Checking Axial Play
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