11 25 530 Removing And Installing/Replacing All Pistons (N12)

WARNING: This page is about a different car, the 2008 MINI Cooper and 2007 MINI Cooper. However, it is still accessible from the selected car via links, so may be relevant.

Special tools required:

00 9 120
11 9 620
11 9 670

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

IMPORTANT: If pistons, connecting rods and bearing shells are reused, they must be reinstalled in the same places.
connecting rods and connecting rod bearing caps are denoted with the same pairing letters; mixing them up will result in engine damage.
Piston and gudgeon 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 Wall

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NOTE: Mark all pistons and conrods with a pen prior to removing.

Example N14:

Direction of arrow (1) points to camshaft drive.

Cylinder allocation (2) per cylinder.

Fig 2: Identifying Camshaft Points

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NOTE: Mark all pistons and conrods with a pen prior to removing.

Example:

Mark cylinder allocation (1) per cylinder.

Direction of arrow (2) points to camshaft drive.

Fig 3: Identifying Camshaft Bearing Positions

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Release connecting rod bolts (1).

Tightening torque: See ENGINE - TIGHTENING TORQUES .

Remove conrod bearing cap.

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

Fig 4: Identifying Connecting Rod Bolts

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Attach special tool 11 9 620 in conrod big end.

Press out connecting rod and piston to cylinder head side.

Fig 5: Identifying Special Tool (11 9 620)

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WARNING: Protective goggles must be worn for the next work step.

WARNING: Protective goggles must be worn.

IMPORTANT: Piston and gudgeon pins are paired and must not be fitted individually.

Lever out piston pin circlip with a screwdriver in direction of arrow.

Fig 6: Identifying Piston Pin

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If necessary, replace connecting rods.

Installation:

The gudgeon 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 Gudgeon 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 gudgeon pin.

Piston diameter at measuring point A.

Fig 8: Identifying Piston Diameter

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Adjust micrometer to cylinder bore of engine block. Set internal calliper 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 Cylinder Bore Diameter

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Install all piston rings.

Install all bearing shells.

Coat piston and piston rings with oil.

Pre-install piston in special tool 11 9 670 .

Screw special tool 11 9 620 into conrod.

Installation:

Check protective lugs on special tool 11 9 620 for correct position and damage.

Fig 10: Identifying Special Tool (11 9 620 And 11 9 670)

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Insert piston with connecting rod in cylinder.

IMPORTANT: Danger of piston ring failure.
Press in piston with finger pressure only, do not drive in (see arrows).

Insert piston (1) so that arrow on piston crown points to camshaft drive.

If reusing the pistons, assign cylinder allocation (2) to correct cylinder.

Press in piston with special tool 11 9 670 .

Fig 11: Pressing Piston With Special Tool (11 9 670)

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IMPORTANT: Point of fracture (1) on conrod.
Conrod and conrod bearing cap are identified with pairing letters (2) 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 .

Both pairing letters (2) must be together on one side.

Fig 12: Identifying Bearing Cap Pairing Letters

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Apply a light coat of oil to crank pin.

Assemble connecting rod and crank pin.

Remove special tool 11 9 620 .

Fig 13: Identifying Special Tool (11 9 620)

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

Check cylinder identification markings (1).

Direction of arrow (2) points to camshaft drive.

Fig 14: Identifying Camshaft Bearing Positions

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Install new connecting rod bolts (1).

Carry out torsion angle tightening of conrods with special tool 00 9 120 .

Tightening torque: See ENGINE - TIGHTENING TORQUES .

Fig 15: Identifying Connecting Rod Bolts

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Assemble engine.