11 25 000 Removing and installing or replacing all pistons (B48, B46)

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2019 MINI Cooper, 2018 MINI Cooper, 2017 MINI Cooper, 2016 MINI Cooper, and 2015 MINI Cooper. However, it is still accessible from the selected car via links, so may be relevant.

Special tools required:

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

Necessary preliminary tasks:

Remove ENGINE with transmission

Remove TRANSMISSION
Mount engine on ASSEMBLY STAND
Remove CYLINDER HEAD .
Remove OIL-/VACUUM PUMP

Attention !

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

Removal:

Unscrew all bolts.

Remove reinforcement (1).

Fig 1: Locating Reinforcement Bolts

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Attention !

Position crankshaft (1) vertically.

Proceed with care at the cylinder wall and oil spray nozzles Risk of damage !

Fig 2: Crankshaft Position

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Undo the connecting rod bolt (1).

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

Fig 3: Connecting Rod Bolt And Connecting Rod Bearing Caps

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

Fig 4: Connecting Rod Bearings

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

Fig 5: Screwing Special Tool (11 8 860) In Large Connecting Rod Eye

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Remove piston (1) with connecting rod.

NOTE: Cooper S:

Fixtures (1) for special tool 2 360 584 .

Fig 6: Fixtures For Special Tool (2 360 584) - Cooper S

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NOTE: Cooper JCW:

Fixtures (1) for special tool 2 360 584 .

Fig 7: Fixtures For Special Tool (2 360 584) - Cooper JCW

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

NOTE: Ø for fixtures (1) = 12 mm.

Fig 8: Preparing Special Tool (2 360 584) With Fixtures

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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 .

Fig 9: Positioning Piston With Connecting Rod On Special Tool (2 360 584)

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WARNING: Safety goggles must be worn.

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

Attention !

Piston and gudgeon pin are matched to each other.

Fig 10: Lifting Off Gudgeon Pin Circlip From Piston Over Groove Using Special Tool (11 4 492)

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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.

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

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

Fig 11: Checking Gudgeon Pin

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Result:

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

Measure:

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

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

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

Fig 12: Piston And Gudgeon Pin

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Engine	Gudgeon pin length	Part number
B48 ML	51.00 mm	8 657 760
B48 ML	55.00 mm	8 638 448
B48/B46 OL	55.00 mm	8 638 450

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 gudgeon pin.

Distance A,

REFER TO TECHNICAL DATA .

Fig 13: Measuring Piston Installation Clearance

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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.

Diameter of the cylinder bore,

TECHNICAL DATA .

Piston installation clearance,

TECHNICAL DATA .

Fig 14: Checking Diameter Of Cylinder Bore

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Permitted total wear clearance,

TECHNICAL DATA .

Clean and oil connecting rod bearing.

Fig 15: Pressing Gudgeon Pin

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If necessary, replace CONNECTING ROD BEARING .

Attention !

Piston and gudgeon 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.

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

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 .

Fig 16: Positioning Piston With Connecting Rod On Special Tool (2 360 584)

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

Fig 17: Pre-Tensioning Gudgeon Pin Circlip In Special Tool (2 360 584)

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NOTE: Make sure the tool is positioned correctly.

Fig 18: Checking Tool Correct Installation Position

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Attention !

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

Fig 19: Inserting Circlip In Way That Opening Points Towards Piston Crown

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Attention !

Risk of damage on piston and gudgeon pin!

Drive in gudgeon pin circlip in the direction of the arrow by means of slight hammer blows.

Fig 20: Driving In Gudgeon Pin Circlip

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Align contact points of PISTON RINGS (offset at approx. 120°, but do not arrange over gudgeon 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.

Fig 21: Preparing Piston With Piston Rings On Special Tool (11 6 240)

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Attention !

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).

Fig 22: Nozzles And Screw

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NOTE: Pay attention to the protective edge for the cylinder wall.

Insert piston so that the arrow points in direction of cylinder 1.

Position piston with connecting rod in special tool 11 6 240 and insert into cylinder.

Fig 23: Positioning Piston With Connecting Rod In Special Tool (11 6 240)

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Attention !

Risk of piston ring breakage.

Risk of damage to oil spray nozzle.

Only press pistons in with finger force - do not knock in!

Slide connecting rod eye onto crankshaft.

Remove special tool 11 8 860 from large connecting rod eye.

Fig 24: Screwing Special Tool (11 8 860) In Large Connecting Rod Eye

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Insert CONNECTING ROD BEARING SHELL (1) into connecting rod bearing cap (2).

Fig 25: Connecting Rod Bearing Shell And Connecting Rod Bearing Cap

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Clean and oil connecting rod bearing.

If necessary, replace CONNECTING ROD BEARING .

Mount connecting rod bearing caps so that pairing letters (1) match.

Fig 26: Connecting Rod Bearing Caps Pairing Letters

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NOTE: Replace connecting rod bolt (1).

Tighten connecting rod bolts (1).

Tightening torque: 11 24 1AZ .

Fig 27: Connecting Rod Bolt And Connecting Rod Bearing Caps

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NOTE: Replace screws.

Install reinforcement (1).

Tighten down all screws.

Tightening torque: 11 41 3AZ/4AZ .

Fig 28: Locating Reinforcement Bolts

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Required follow-up work:

Check engine function and check for leak tightness.