11 21 531 Replacing all crankshaft main bearings (N54, N54T)

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

Special tools required:

IMPORTANT: Aluminium screws/bolts must be replaced each time they are released .
Aluminium screws/bolts are permitted with and without colour coding (blue).
For reliable identification:

Aluminium screws/bolts are not magnetic .

Jointing torque and angle of rotation must be observed without fail (risk of damage) .

Necessary preliminary tasks:

Remove CRANKSHAFT

Check setting of oil spray nozzles, adjusting if necessary:

Attach special tool 11 8 510 to main bearing screw connection, secure with bolt (1).

Installation note:

The oil nozzle must be located precisely in the groove of special tool 11 8 510 .

If necessary, adjust oil nozzle.

Fig 1: Installing Special Tool (11 8 510) With Crankshaft Main Bearing Screw Connection

Adjust oil nozzle.

Release screw (1).

Tightening torque 11 11 5AZ .

Fig 2: Identifying Oil Nozzle Screw

Remove bearing shells (2) and (3).

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

Fig 3: Removing Bearing Shells

Installation note:

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

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

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

Fig 4: Identifying Bearing Shell With And Without Lubricant Groove

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

Observe bearing classification.

Bearing classification (2) of CONNECTING RODS code letters b and r.

Fig 5: Identifying Main Bearing And Connecting Rod Classification Numbers

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

Installation note:

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

Fig 6: Identifying Crankcase Main Bearing Classification

Installation note:

The letter/number combination produces a bearing shell pairing.

Identification by different colours.

IMPORTANT: First bearing position is on the timing drive.
The colour 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) colour Yellow.

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

Code letter C = bearing shell (1) colour 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 colour combination Yellow and Red must not be fitted; the bearing colours Green/Green must be selected for this colour combination, see table.

Fig 7: Identifying Bearing Shell With And Without Lubricant Groove

Installation example:

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

Bearing 2: A and 2 colours Yellow and Green.

Bearing 3: B and 2 colours Green and Green.

Bearing 4: C and 2 colours Red and Green.

Bearing 5: B and 1 colours Green and Yellow.

Bearing 6: C and 3 colours Red and Red.

Bearing 7: C and 1 colours Green and Green.

Fig 8: Identifying Bearing Shell With And Without Lubricant Groove

The colour combination Yellow and Red must not be fitted.

Installation note:

Possible colour combinations for mounting the crankshaft in the crankcase.

(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

Insert all bearing shells (2 and 3).

IMPORTANT: Clean sealing surfaces.
Do not clean sealing faces with a metal-cutting tool.

Fig 9: Installing Bearing Shells

Only use special tool 11 4 470 to clean sealing surfaces.

Determine bearing play with special tool 00 2 590 .

Installation note:

All measuring points must be free from oil and grease.

Use used screws to determine bearing play.

Set up crankcase lower section (bedplate) with bearing shells.

Remove crankcase lower section (bedplate).

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

Crankshaft bearing play radial .

Installation note:

Remove Plastigage.

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

Fig 10: Locating Plastigage

Install crankcase lower section (bedplate).

Assemble engine.