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

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

Special tools required:

00 2 590 PLASTIGAGE (5)
11 4 251
11 4 252
11 4 470

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 .
The end faces of aluminum screws/bolts are painted blue for the purposes of reliable identification.
Jointing torque and angle of rotation must be observed without fail (risk of damage) .

Necessary preliminary tasks:

Remove crankshaft, see 11 21 500 Replacing crankshaft (N52K)

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, see 11 11 CRANKCASE .

Fig 1: Oil Spray Nozzle, Special Tools (11 4 251) And (11 4 252)

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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.

Fig 2: Bearing Shells

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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.

Fig 3: Bearing Shells

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IMPORTANT: It is not possible to remachine the crankshaft.

Surface (1) for marking.

Seven-digit part number (2).

Bearing classification (3) on bedplate (see table: values of 1/2/3).

Fig 4: Bearing Classification On Bedplate

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Bearing classification (1) on crankcase (see table: values of A/B/C).

Installation:

When all the letters and number code have been determined, the color of the bearing shells must be allocated (see table).

IMPORTANT: Excessively small bearing play will result in engine damage.
The color combination Yellow and Red must not be fitted.
Possible color combinations (see table).

Fig 5: Bearing Classification On Crankcase

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BEARING SHELL COLOR COMBINATIONS SPECIFICATION

(A1) Bedplate / Yellow	(B1) Bedplate / Yellow	(C1) Bedplate / Green
(A1) Crankcase / Yellow	(B1) Crankcase / Green	(C1) Crankcase / Green
(A2) Bedplate / Green	(B2) Bedplate / Green	(C2) Bedplate / Green
(A2) Crankcase / Yellow	(B2) Crankcase / Green	(C2) Crankcase / Red
(A3) Bedplate / Green	(B3) Bedplate / Red	(C3) Bedplate / Red
(A3) Crankcase / Green	(B3) Crankcase / Green	(C3) Crankcase / 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 6: Bearing Shells

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Use the existing screws to determine the bearing play.

Set up bedplate with bearing shells, see 11 21 500 Replacing crankshaft (N52K) .

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 7: Reading Bearing Play At Width Of Flattened Plastic Thread And Measurement Scale

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Install bedplate11 21 500 Replacing crankshaft (N52K) .

Assemble engine.