Removing and installing/replacing all pistons (B48 and B46 engine) (Cooper S)

Special tools required:

11 8 860
2 360 584
11 4 492
11 6 240

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

Preliminary work needed:

Remove ENGINE with transmission
Vehicles with automatic transmission: Remove transmission.
- Up to model year 2019, refer to REMOVING AND INSTALLING TRANSMISSION (AISIN F21FT) .
- As of model year 2020, refer to REMOVING AND INSTALLING AUTOMATIC TRANSMISSION (AISIN GA8G45) .
Vehicles with manual transmission: Remove transmission.
- Refer to REMOVING AND INSTALLING TRANSMISSION (GS6-59BG/DG) (COOPER S AND JOHN COOPER WORKS) .
Mount ENGINE ON ASSEMBLY JIG .
Remove CYLINDER HEAD .
Remove oil pump and vacuum pump. Refer to REMOVING AND INSTALLING OR REPLACING OIL PUMP (B48 AND B46 ENGINE) (COOPER S AND JOHN COOPER WORKS) and REMOVING AND INSTALLING OR REPLACING VACUUM PUMP (B48 AND B46 ENGINE) (COOPER S AND JOHN COOPER WORKS) .

IMPORTANT: If pistons, connecting rods and connecting rod bearing shells are reused, they must be reinstalled in the same places.
Individual connecting rod replacement is not permitted; they are classified by weight class.

Connecting rods and connecting rod bearing caps are denoted with the same pairing letters. Mixing up the components will result in engine damage.

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

When replacing a piston, all other pistons absolutely must be replaced as well.

Replacing a single piston is not permitted!

Removal:

Unscrew all bolts.

Remove reinforcement (1).

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IMPORTANT: Position crankshaft (1) vertically.
Proceed with vehicle care at the cylinder wall and oil spray nozzles Risk of damage!

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Undo the connecting rod bolt (1).

Remove connecting rod bearing caps (2) and set down in neat order.

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Remove connecting rod bearings (1) and set down in neat order.

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Screw special tool 11 8 860 in at large connecting rod eye.

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Remove piston (1) with connecting rod.

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NOTE: Stands (1) for special tool 2 360 584.

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Prepare special tool 2 360 584 with stands (1).

NOTE: Ø for stands (1) = 12.5 mm.

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WARNING: Safety goggles must be worn for the next operation.

Position piston (1) with connecting rod (2) on special tool 2 360 584.

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WARNING: Safety goggles must be worn.

Lift off piston pin circlip (1) from piston over groove (2) using special tool 11 4 492.

IMPORTANT: Piston and piston pin are matched to each other.
They must not be mixed up.
Pay attention to installation position of piston and connecting rod.
Piston and connecting rod must not be installed with a rotational misalignment of 180 degree to each other.

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Check if the piston pin (1) has noticeable play in the piston.

Check whether piston pin (1) can be removed without excessive force.

Result:

Piston pin (1) is very difficult to remove or has noticeable play.

Measure:

Replace the piston (2) and piston pin (1).

Remove piston pin (1) from piston (2) and connecting rod (3) in the direction of the arrow.

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The piston pin length must be determined in order to replace the piston:

engine	Piston pin length	Part number
B48M0	51.00 mm	8 657 760
B48M0	55.00 mm	8 638 448
B48/B46 M0	55.00 mm	8 638 450
B48 M0 China	52.00 mm	8 623 260
B48 M0 China	55.00 mm	8 632 624

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Installation:

Before installation, measure piston installation clearance. Measure piston diameter with caliper gauge at measuring point A from lower edge of piston and offset at 90° to the axis of the piston pin.

Refer to TECHNICAL DATA .

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

For diameter of the cylinder bore, piston installation clearance, and permissible total wear clearance: refer to TECHNICAL DATA .

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Clean and oil connecting rod bearing.

If necessary, replace CONNECTING ROD BEARING .

NOTE: It must be possible to the press piston pin (1) through the connecting rod (small connecting rod eye) with little force; it must not reveal any noticeable play.

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WARNING: Safety goggles must be worn for the next operation.

Position connecting rod (2) in piston (1).

Position piston (1) with connecting rod on special tool 2 360 584.

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Pre-tension piston pin circlip (1) in special tool 2 360 584.

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NOTE: Make sure the tool is positioned correctly.

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IMPORTANT: Insert the circlip (1) in a way that the opening (2) points towards the piston crown.

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IMPORTANT: Risk of damage on piston and piston pin!

Drive in piston pin circlip in the direction of the arrow by means of slight hammer fuses.

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Align contact points of PISTON RINGS (offset at approx. 120°, but do not arrange over piston pin boss).

Coat piston (1) and piston rings with oil.

Prepare piston (1) with piston rings on special tool 11 6 240.

Screw special tool 11 8 860 on at large connecting rod eye.

NOTE: Make sure CONNECTING ROD BEARING (2) is in proper installation position.

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IMPORTANT: Oil spray nozzles (2) must not be maladjusted or bent.
A bent oil spray nozzle cannot be adjusted and must be replaced.
Release screw (1) and remove oil spray nozzle (2).
Tightening torque 11 42 10AZ .