11 21 531 Replacing all main crankshaft bearing shells (N52K)

WARNING: This page is about a different variant/trim than selected.

IMPORTANT: Aluminium-magnesium materials.
No steel screws/bolts may be used due to the threat of electrochemical corrosion.
A magnesium crankcase requires aluminum screws/bolts exclusively.
Aluminum screws/bolts must be replaced each time they are released .
Aluminum screws/bolts are permitted with and without color coding (blue).
For reliable identification:
Aluminum screws/bolts are not magnetic .
Jointing torque and angle of rotation must be observed without fail (risk of damage) .

Necessary preliminary tasks:

Remove CRANKSHAFT

Checking position of oil spray nozzles

Insert special tool 11 4 251 in screw connection of main bearing.

NOTE: Special tool 11 4 252 must be pre-installed at the seventh main bearing.

Check position of oil spray nozzle (2) according to position (1) on special tool 11 4 251.

If necessary, adjust and secure oil spray nozzle (2).

Tightening torque 11 11 5AZ .

Fig 1: Identifying Oil Spray Nozzle On Special Tool 11 4 251

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Remove bearing shells (2) and guide bearing shell (3).

NOTE: Guide bearing shell (3) is a thrust bearing.

Observe bearing classification See ENGINE BLOCK, CYLINDER CRANKCASE N52K/B30 ; ENGINE BLOCK, CYLINDER CRANKCASE N52K/B25 ; CRANKSHAFT AND BEARINGS ; CRANKSHAFT AND BEARINGS ; CRANKSHAFT AND BEARINGS N52K/B30 ; CRANKSHAFT AND BEARINGS N52K/B25 ; CRANKSHAFT AND BEARINGS N52K/B30 or CRANKSHAFT AND BEARINGS N52K/B25 .

Fig 2: Checking Bearing Play

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Installation:

Bearing shell (1) with lubricant groove must be fitted in crankcase.

Bearing shell (2) without lubricant groove must be fitted in bedplate.

IMPORTANT: Allocation of bearing points:
Bearing point 1 is at the front on the timing chain drive in the direction of travel.

Fig 3: Identifying Bearing Shell With/Without Lubricant Groove

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Surface (1) for identification on crankshaft web 1.

Seven-digit part number (2).

Main bearing classification (3) for crankcase lower half (bedplate), code numbers 1 2 3, see table.

NOTE: Code letters (4 and 5) are exclusively required for a machined crankshaft.

Code letter (4) as per table, main bearing.

B= build date 1 (B 1 2 3 -0.25 mm).

B= build date 2 (C 1 2 3 -0.50 mm).

Code letter (5) as per table, lift bearing.

Fig 4: Identifying Seven Digit Code On Crankshaft Web Surface

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B= construction stage 1 (-0.25 mm).

C = construction stage 2 (-0.50 mm)

Observe bearing classification See CRANKSHAFT AND BEARINGS ; CRANKSHAFT AND BEARINGS ; CRANKSHAFT AND BEARINGS N52K/B30 ; CRANKSHAFT AND BEARINGS N52K/B25 ; CRANKSHAFT AND BEARINGS N52K/B30 or CRANKSHAFT AND BEARINGS N52K/B25 .

Main bearing classification (1) in crankcase, code letters A/B or C, see table.

Installation:

When all the letters and number code have been determined, the bearing shell color must be allocated, see table.

Fig 5: Identifying Bearing Classification Of Crankcase Upper Section

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Installation:

The letter/number combination produces a bearing shell pairing.

Identification by different colors.

IMPORTANT: First bearing point is on the timing drive.
The color combination Yellow and Red must not be fitted.
Engine damage will result if excessively small bearing play is determined.

Code letters on crankcase

Code letter A = bearing shell (1) color Yellow.

Code letter B = bearing shell (1) color Green.

Code letter C = bearing shell (1) color Red.

Code numbers on crankshaft:

Code number 1 = bearing shell (2) Yellow.

Code number 2 = bearing shell (2) Green.

Code number 3 = bearing shell (2) Red.

IMPORTANT: The color combination Yellow and Red must not be fitted; the bearing colors Green/Green must be selected for this color combination, see table.

Fig 6: Identifying Bearing Shell With/Without Lubricant Groove

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Installation example

For bearing 1 with code letter A on the crankcase and code number 1 on the crankshaft bearing shell (1) with the color Yellow is required for the crankcase and bearing shell (2) with the color Yellow for the crankcase lower half (bedplate).

Bearing 2: A and 2 colors Yellow and Green.

Bearing 3: B and 2 colors Green and Green.

Bearing 4: C and 2 colors Red and Green.

Bearing 5: B and 1 colors Green and Yellow.

Bearing 6: C and 3 colors Red and Red.

Bearing 7: C and 1 colors Green and Green.

The color combination Yellow and Red must not be fitted.

Fig 7: Identifying Bearing Shell With/Without Lubricant Groove

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Installation:

Possible color combinations for mounting the crankshaft in the crankcase.

CRANKSHAFT COLOR REFERENCE CHART

(A 1) Crankcase/Yellow	(B 1) Crankcase/Green	(C 1) Crankcase/Green
(A 1) Crankcase lower half/Yellow	(B 1) Crankcase lower half/Yellow	(C 1) Crankcase lower half/Green

(A 2) Crankcase/Yellow	(B 2) Crankcase/Green	(C 2) Crankcase/Red
(A 2) Crankcase lower half/Green	(B 2) Crankcase lower half/Green	(C 2) Crankcase lower half/Green

(A 3) Crankcase/Green	(B 3) Crankcase/Green	(C 3) Crankcase/Red
(A 3) Crankcase lower half/Green	(B 3) Crankcase lower half/Red	(C 3) Crankcase lower half/Red

Install bearing shells (2) and guide bearing shell (3).

Installation:

Clean all sealing surfaces.

IMPORTANT: Do not use any metal-cutting tools.

Clean sealing faces with special tool 11 4 470 only.

Determine bearing play with special tool 00 2 590.

Installation:

All measuring points must be clean and free from oil and grease. If necessary, clean all measuring points.

Fig 8: Checking Bearing Play

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Use the existing screws to determine the bearing play.

Set up BEDPLATE with bearing shells.

Remove bedplate.

Read off bearing play at width of flattened plastic thread and measurement scale.

Installation:

Remove plastic thread.

Apply a light coat of oil to bearing shells and crankshaft.

Fig 9: Checking Radial Clearance At Width Of Flattened Plastic Thread (Plastigage)

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Install BEDPLATE .

Assemble engine.