11 25 530 Removing And Installing/Replacing All Pistons (N62TU)

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

Special tools required:

00 9 120
11 5 430
11 5 440
11 5 450

IMPORTANT: Re-install piston, conrod and bearing shells back in the same position and in the same installation location.
Conrods and conrod bearing caps are denoted with the same pairing letters, do not mix them up.

Necessary preliminary tasks:

(engine removed)
Install engine on assembly stand.
Remove both cylinder heads . See 11 12 105 REMOVING AND INSTALLING LEFT CYLINDER HEAD (N62 FROM 9/03 AND N62TU) and 11 12 106 REMOVING AND INSTALLING RIGHT CYLINDER HEAD (N62 FROM 9/03 AND N62TU) .
Removing oil pan . See 11 13 010 REMOVING AND INSTALLING/REPLACING OIL SUMP TOP SECTION (N62/N62TU) and 11 13 020 REMOVING AND INSTALLING/REPLACING OIL SUMP BOTTOM SECTION (N62/N62TU) .
Remove oil pump . See 11 41 000 REMOVING AND INSTALLING/REPLACING OIL PUMP (N62) .

In event of heavy oil carbon residue:

Carefully remove oil carbon residue from cylinder wall.

Fig 1: Locating Oil Carbon Residue From Cylinder Wall

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IMPORTANT: When removing and installing pistons, make sure piston cooling spray nozzles (1) are not damaged.

Fig 2: Identifying Piston Cooling Spray Nozzles

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Unscrew conrod bearing cover.

IMPORTANT: Conrods and conrod bearing caps are denoted with the same pairing letters.
Set down conrod bearing caps in order.

Fig 3: Locating Conrod Bearing Cover

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Insert special tool 11 5 440 in conrod.

Screw special tool 11 5 440 into conrod with screw (1).

Remove conrod with piston from cylinder head side.

Fig 4: Identifying Special Tool (11 5 440) And (11 5 440)

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IMPORTANT: Piston and piston pin are matched to each other.
Mixing up the components will result in engine damage.

Lever out circlip with special tool 11 4 492 in direction of arrow and press out piston pin.

Fig 5: Identifying Special Tool (11 4 492)

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If necessary, replace connecting rods.

NOTE: The conrods can also be replaced individually.

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 6: Pressing Piston Pin

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Prior to installation, measure piston installation clearance:

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

Measuring point A . See ENGINE - TECHNICAL DATA - V8 (N62TU) .

Fig 7: Measuring Piston Diameter With Micrometer

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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 . See ENGINE - TECHNICAL DATA - V8 (N62TU) .

Piston installation clearance . See ENGINE - TECHNICAL DATA - V8 (N62TU) .

Total permissible wear tolerance . See ENGINE - TECHNICAL DATA - V8 (N62TU) .

Fig 8: Identifying Micrometer To Cylinder Bore Of Engine Block

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NOTE: The pistons and conrods of cylinders 1 to 8 are identical.

IMPORTANT: The conrods of cylinder banks 1 to 4 and 5 to 8 are mounted to the pistons differently.

Cylinder bank 1 to 4

Mount conrod on piston in such a way that arrow on piston points upwards and marking on conrod points upwards .

Fig 9: Identifying Piston Marking On Conrod Points

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Cylinder bank 5 to 8

Mount conrod on piston in such a way that arrow on piston points downwards and marking on conrod points upwards .

Install conrod bearing . See 11 24 571 REPLACING ALL CONROD BEARINGS (N62/N62TU) .

Fig 10: Identifying Piston Marking On Conrod Points

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Install retaining ring.

Fig 11: Installing Retaining Ring

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Offset the contact points (1) of the piston rings by approx. 120° to each other but do not position above the piston pin boss.

NOTE: See illustration.
Illustration shows N52.

Fig 12: Identifying Contact Points Of Piston Rings

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Installation:

B40 and B48:

Insert special tools 11 5 440 in conrod.

Installation:

B40:

Prepare piston with rings with special tool 11 5 450 .

Fig 13: Identifying Special Tool (11 5 440) And (11 5 450)

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B40:

Lightly coat pistons and piston rings with oil. Offset the contact points of the piston rings by approx. 120° to each other but do not position above the piston pin boss.

Slide in special tool 11 5 450 with piston (1).

Install piston so that arrow points to camshaft drive.

IMPORTANT: Danger of piston ring failure.

Press in piston with finger force only.

Fig 14: Identifying Special Tool (11 5 450)

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B48:

Keep piston rings compressed with special tool 11 5 430.

Install piston so that arrow points to camshaft drive.

IMPORTANT: Danger of piston ring failure.

Press in piston with finger force only.

Fig 15: Identifying Special Tool (11 5 430)

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Attach crankpin to connecting rod.

Remove special tools 11 5 450 .

Fig 16: Identifying Special Tool (11 5 440) And (11 5 440)

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NOTE: For purposes of clarity, the pairing letters (1) are shown on the removed conrod.

IMPORTANT: Conrods and conrod bearing caps are denoted with the same pairing letters (1), do not mix them up.

Fig 17: Identifying Conrods And Conrod Bearing Caps Denoted With Pairing Letters

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IMPORTANT: Conrod of cylinder 1 to 4 is installed in direction of travel, see arrow (1), front.
Conrod of cylinder 5 to 8 is installed in direction of travel, see arrow (1), rear.
Markings on conrod must be situated on the outside (see arrows)
Incorrect assembly will result in engine damage.

Apply light coat of oil to connecting-rod bearing shells.

Fit bearing cap so that pairing letters match up.

Install new conrod bolts.

Fig 18: Identifying Conrod Of Cylinder Of Travel

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Secure conrod with special tool 00 9 120 .

Tightening torque 11 24 1AZ . See ENGINE - TIGHTENING TORQUES (N62TU V8) .

Fig 19: Identifying Special Tool (00 9 120)

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Assemble engine.