11 25 530 Removing and Installing/Replacing All Pistons (N54)

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Special tools required:

00 9 120
11 5 464
11 8 141
11 8 560
11 8 561
11 8 562
11 8 563
11 8 590

WARNING: Protective goggles must be worn when working on the piston pin circlip.

IMPORTANT:

If pistons, conrods and bearing shells are reused, they must be reinstalled in the same places.

Individual conrod replacement is not permitted; they are classified according to weight categories.

Conrods and conrod bearing caps are denoted with the same pairing letters; mixing them up will result in engine damage.

Piston and piston pins are paired and must not be fitted individually.

Necessary preliminary tasks:

Remove engine.
Mount engine on assembly stand.
Remove intake air manifold.
Remove cylinder head.
Remove engine oil sump.
Remove oil pump.

NOTE:

In event of heavy oil carbon residue:

Carefully remove oil carbon residue from cylinder wall.

NOTE: Illustrations show N46.

Fig 1: Locating Cylinder Oil Carbon

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Do not release screw (1).

Oil spray nozzle (2) must not be maladjusted or bent.

If necessary, readjust (risk of damage).

Fig 2: Locating Oil Spray Nozzle & Screw

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Release conrod bolts (1).

Tightening torque, see 11 24 1AZ in ENGINE -- TORQUE SPECIFICATIONS -- TWIN TURBO

Remove conrod bearing cap (2) in direction of arrow.

IMPORTANT: Conrods and conrod bearing caps are denoted with the same pairing letters; mixing them up will result in engine damage.

Fig 3: Identifying Bearing Cap & Bolts

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Screw special tool 11 8 590 into conrod big end. See 11 8 590 INSERTION TOOL

Press out conrod and piston to cylinder head side.

IMPORTANT: Risk of damage to oil spray nozzle.

Fig 4: Identifying Special Tool (11 8 590) Into Conrod Big

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Preliminary work:

Clamp special tool 11 8 561 in a vice.

Secure piston (1) with conrod to special tool 11 8 561.

Fig 5: Identifying Special Tool (11 8 561) With Piston

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WARNING:

Protective goggles must be worn for the next work step.

Protective goggles must be worn.

To lever out piston circlip (1), support special tool 11 5 464 on piston (2).

Lever out piston circlip (1) with special tool 11 5 464 in direction of arrow.

Fig 6: Identifying Special Tool (11 5 464) With Piston Circlip

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If necessary, replace connecting rods.

IMPORTANT:

Connecting rods are divided into weight categories and are only available as a set.

Old and new connecting rods must not be installed in mixed combinations.

Installation:

The piston pin must be able to be pressed through the liner by hand with little force and must not display any significant play.

Fig 7: Identifying Piston Pin

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Measure piston installation clearance:

Measure piston diameter with micrometer at measuring point A from bottom edge of piston and offset at 90° to the axis of the piston pin.

Piston diameter at measuring point A.

Fig 8: Identifying Piston Diameter Measuring Point

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Adjust micrometer to cylinder bore of engine block. Set internal caliper on micrometer to zero. Measure bottom, center and top of cylinder bore in direction of travel and direction of engine rotation.

Diameter of cylinder bore.

Piston installation clearance.

Total permissible wear tolerance.

If necessary, replace piston.

Fig 9: Identifying Diameter Of Cylinder Bore

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WARNING: Protective goggles must be worn.

IMPORTANT: The opening of the piston pin circlip must be installed in the 6 o'clock position on the piston - risk of damage .

Insert piston circlip (2) into groove of special tool 11 8 562.

Bring piston circlip (2) into assembly position (1).

Fig 10: Inserting Piston Circlip Into Groove Of Special Tool (11 8 562)

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WARNING: Protective goggles must be worn.

Slide special tool 11 8 563 up to piston pin circlip (2)

Special tools 11 8 562 and 11 8 563 are prepared.

Fig 11: Identifying Special Tools (11 8 562 & 11 8 563)

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WARNING: Protective goggles must be worn.

Cutout on special tool 11 8 562 must point to piston crown; only then can special tool 11 8 563 be correctly fitted.

When special tools 11 8 562 and 11 8 563 are correctly positioned, the piston pin circlip must be driven in with a plastic hammer in the direction of the arrow.

NOTE: See Fig 12 .

Fig 12: Identifying Special Tool (11 8 562) To Piston Crown

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Piston pin circlip is correctly installed when opening (1) points downwards.

Fig 13: Locating Piston Pin Circlip

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NOTE: B 30.

Install all piston rings.

Install all bearing shells.

Coat piston and piston rings with oil.

Pre-install piston (2) in special tool 11 8 141.

Screw on special tool 11 8 590 in connecting rod (2). See 11 8 590 INSERTION TOOL

Installation:

Check protective lugs (1) on special tool 11 8 590 for correct position and damage. See 11 8 590 INSERTION TOOL

Fig 14: Identifying Piston In Special Tool (11 8 141)

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Insert piston with conrod in cylinder.

IMPORTANT:

Risk of damage to oil spray nozzle.

Danger of piston ring failure.

Press in piston in direction of arrow with finger pressure only, do not drive in.

Insert piston so that arrow on piston crown points to camshaft drive.

Press in piston (1) with special tool 11 8 141.

Fig 15: Identifying Piston In Special Tool (11 8 141)

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IMPORTANT:

Conrod and conrod bearing cap are identified with pairing letters (1) and must not be mixed up.

Mixing them up or incorrectly fitting the conrod bearing cap on the big end will result in engine damage.

Fig 16: Identifying Mark On Bearing Cap

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Apply a light coat of oil to crank pin.

Assemble conrod and crank pin.

Screw off special tool 11 8 560 in counterclockwise direction. See 11 8 560 REMOVAL AND INSTALLATION KIT

Fig 17: Identifying Special Tool (11 8 560) On Crank Pin

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Fit bearing caps (2) so that pairing letters match up.

Install new conrod bolts (1).

Tightening torque, see 11 24 1AZ in ENGINE -- TORQUE SPECIFICATIONS -- TWIN TURBO

Fig 18: Identifying Bearing Caps & Bolts

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Adjust torsion angle of conrod with special tool 00 9 120 (see Fig 19 ).

Tightening torque, see 11 24 1AZ in ENGINE -- TORQUE SPECIFICATIONS -- TWIN TURBO

Fig 19: Identifying Special Tool (00 9 120)

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Assemble engine.