Removing and installing or replacing all pistons (B36 engine) (Cooper base)

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.

IMPORTANT: The piston diameter depends on the engine version!

B38 AU12 Lower performance class for piston diameter 78 mm
B38 AM15 Medium performance class for piston diameter 82 mm

Preliminary work needed:

Remove ENGINE with transmission
Remove transmission.
- Vehicles with automatic transmission, refer to REMOVING AND INSTALLING TRANSMISSION (AISIN F21FT)
- Vehicles with manual transmission, refer to REMOVING AND INSTALLING TRANSMISSION (GS6-58BG) .
Mount ENGINE ON ASSEMBLY JIG .
Remove CYLINDER HEAD .
Remove the OIL PUMP .

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.

Removal:

Unscrew the screws (1).

Remove reinforcement (2).

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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 difficult to remove or piston pin (1) has noticeable play.

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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
B38/B48 ML EPS 11.0	51.00 mm	8 657 760
B38/B48 ML EPS 11.0	55.00 mm	8 638 448
B48/B46 OL EPS 10.2	55.00 mm	8 638 450
B38/B48 ML China EPS 11.0	52.00 mm	8 623 260
B38/B48 ML China EPS 11.0	55.00 mm	8 632 624
B48 OL China EPS 10.2	52.00 mm	8 623 261
B48 OL China EPS 10.2	55.00 mm	8 632 626
B38 TOP EPS 9.5	55.00 mm	8 618 504

Installation:

Before installation, measure piston installation clearance. Measure piston diameter with micrometer screw 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 micrometer screw to cylinder bore of engine block. Set internal measuring device at micrometer screw 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 permitted total wear clearance: refer to TECHNICAL DATA .

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Clean and oil connecting rod bearing.

If necessary, replace CONNECTING ROD BEARING .

IMPORTANT: 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 piston pin (1) through the connecting rod (small connecting rod eye) with little force; it must not reveal any noticeable play.

Position piston (2) on connecting rod (3).

Install piston pin (1) in piston (2) and connecting rod (3).

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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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Drive in piston pin circlip in arrow direction.

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).

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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.

IMPORTANT: Risk of piston ring breakage.
Risk of damage to oil spray nozzle.
Only press pistons in with finger force - do not knock in!

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Slide connecting rod eye onto crankshaft.

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

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

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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.

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Parts: Replace connecting rod bolt (1).

Tighten connecting rod bolts (1).

Tightening torque: 11 24 1AZ .

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Parts:

Replace reinforcement (2).
Replace screws (1).

Install reinforcement (2).

Tighten down screws (1).

Tightening torque: 11 41 3AZ .

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Required reworking:

Install the OIL PUMP .
Mount the CYLINDER HEAD .
Remove engine from ASSEMBLY JIG .
Install transmission.
- Vehicles with automatic transmission, refer to REMOVING AND INSTALLING TRANSMISSION (AISIN F21FT)
- Vehicles with manual transmission, refer to REMOVING AND INSTALLING TRANSMISSION (GS6-58BG) .
Install ENGINE .
Check engine operation and check for tightness