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Home >> BMW >> 2013 >> Z4 28i, Automatic Trans >> Repair and Diagnosis >> External Pages >> Different car >> Section 1476 (Engine - Pistons, Piston Rings, Balancing Shafts, Rocker Arms, Intake / Exhaust Valves, Valve Springs, Valve Stem Seals, Variable Valve Lift Control System (VALVETRONIC) - Repair) >> Pistons And Piston Rings >> N55 Engine >> 11 25 530 Removing and installing/replacing all pistons (N55)

11 25 530 Removing and installing/replacing all pistons (N55)

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Special tools required: 

WARNING: Safety 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.
Piston and gudgeon pins are paired and must not be fitted individually.
Individual connecting rod replacement is not permitted; they are classified by weight class.
Connecting rods and connecting rod bearing caps are marked with the same pairing letters; mixing them up will result in engine damage.

Necessary preliminary work: 

NOTE: In event of heavy oil carbon residue:

Carefully remove oil carbon residue from cylinder wall.

NOTE: Graphic shows N46.
Fig 1: Locating Carbon Residue On Cylinder Wall
G09920647Courtesy of BMW OF NORTH AMERICA, INC.
IMPORTANT: Do not  release screw (1).
OIL SPRAY NOZZLE (2) must not be maladjusted or bent.
If necessary, readjust (risk of damage)  .
Fig 2: Identifying Oil Spray Nozzle And Screw
G09920648Courtesy of BMW OF NORTH AMERICA, INC.

Release connecting rod bolts (1).

Tightening torque 11 24 1AZ .

Remove connecting rod bearing cap (2).

IMPORTANT: Connecting rods and connecting rod bearing caps are marked with the same pairing letters; mixing them up will result in engine damage.
Fig 3: Identifying Connecting Rod Bearing Cap And Bolts
G09920649Courtesy of BMW OF NORTH AMERICA, INC.

Screw special tool 11 8 590 into big end of connecting rod.

Press out connecting rod and piston to cylinder head side.

IMPORTANT: Risk of damage  to oil spray nozzle.
Fig 4: Installing Special Tool (11 8 590) Into Big End Of Connecting Rod
G09920650Courtesy of BMW OF NORTH AMERICA, INC.

Preliminary work: 

Secure special tool 11 4 491 in vice.

Secure piston (1) with connecting rod to special tool 11 4 491 .

NOTE: Graphic shows N52.
Fig 5: Securing Piston And Connecting Rod To Special Tool (11 4 491)
G09920651Courtesy of BMW OF NORTH AMERICA, INC.
WARNING: Safety goggles  must be worn for the next operation.
WARNING: Safety goggles  must be worn.

To lever out piston circlip (1), support with special tool 11 4 492 on piston (2).

Lever out piston circlip (1) with special tool 11 4 492 in direction of arrow.

Fig 6: Removing Piston Circlip Using Special Tool (11 4 492)
G09920652Courtesy of BMW OF NORTH AMERICA, INC.
IMPORTANT: Connecting rods are divided into weight classes and are only available as a set.
Old and new connecting rods must not be installed in mixed combinations.

Installation note: 

The gudgeon pin must be able to be pressed through the bush by hand with little force and must not display any significant play.

Fig 7: Identifying Gudgeon Pin
G09920653Courtesy of BMW OF NORTH AMERICA, INC.

Measure PISTON INSTALLATION CLEARANCE :

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

Piston diameter at measuring point A.

Fig 8: Measuring Piston Diameter Using Micrometer
G09920654Courtesy of BMW OF NORTH AMERICA, INC.

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

DIAMETER OF CYLINDER BORE .

PERMISSIBLE TOTAL WEAR CLEARANCE .

Installation note: 

If necessary, replace piston  .

Fig 9: Adjusting Micrometer To Cylinder Bore Of Engine Block
G09920655Courtesy of BMW OF NORTH AMERICA, INC.
WARNING: Safety goggles  must be worn.
IMPORTANT: The opening of the piston pin circlip must be installed on the piston in the 6 o'clock position  .
Risk of damage! 

Insert piston circlip (2) into groove of special tool 11 8 562 .

Bring piston circlip (2) into installation position (1).

Fig 10: Identifying Piston Circlip Working Position
G09920656Courtesy of BMW OF NORTH AMERICA, INC.
WARNING: Safety goggles  must be worn.

Slide on special tool 11 8 564 up to piston pin circlip (1)

Special tools 11 8 562 and 11 8 564 are prepared.

Fig 11: Identifying Piston Pin Circlip And Special Tools (11 8 564 And 562)
G09920657Courtesy of BMW OF NORTH AMERICA, INC.
WARNING: Safety goggles  must be worn.

The aperture on special tool 11 8 562 must point to piston crown; only then can special tool 11 8 564 be fitted correctly.

If the special tools 11 8 562 and 11 8 564 are not positioned correctly, the piston pin circlip must be driven in using a plastic hammer in direction of arrow.

NOTE: See Fig 12.
Fig 12: Positioning Special Tools
G09920658Courtesy of BMW OF NORTH AMERICA, INC.

Piston pin circlip is correctly installed when opening (1) points downwards.

Fig 13: Identifying Proper Installation Of Piston Pin Circlip
G09920659Courtesy of BMW OF NORTH AMERICA, INC.

Install all PISTON RINGS .

Install all BEARING SHELLS .

Coat piston and piston rings with oil.

Pre-install piston (2) in special tool 11 8 141 .

Screw on special tool 11 8 590 in connecting rod (2).

Installation note: 

Make sure protective lugs (1) on special tool 11 8 590 are positioned correctly and check for damage.

Fig 14: Installing Piston In Special Tool (11 8 141) And Positioning Protective Lugs Of Special Tool (11 8 590)
G09920660Courtesy of BMW OF NORTH AMERICA, INC.

Insert piston with connecting rod in cylinder.

IMPORTANT: Risk of damage to oil spray nozzle.
Risk of breakage of piston rings.
Press in piston in direction of arrow with finger pressure only, do not drive in.

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

Press in piston (1) with special tool 11 8 141 .

Fig 15: Pressing-In Piston Using Special Tool (11 8 141)
G09920661Courtesy of BMW OF NORTH AMERICA, INC.
IMPORTANT: Connecting rod and connecting rod bearing cap are marked with pairing letters (1) and must not be mixed up.
Swapping or incorrect assembly the connecting rod bearing cap on the big end will result in engine damage  .
Fig 16: Identifying Pairing Letters For Connecting Rod And Bearing Cap
G09920662Courtesy of BMW OF NORTH AMERICA, INC.

Apply a light coat of oil to crankshaft journal.

Assemble connecting rod and crankshaft journal.

Screw off special tool 11 8 590 in counter-clockwise direction.

NOTE: Illustration shows N54.
Fig 17: Installing Special Tool (11 8 590) Into Big End Of Connecting Rod
G09920663Courtesy of BMW OF NORTH AMERICA, INC.

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

Install new connecting rod bolts (1).

Join connecting rod bolts (1).

Tightening torque 11 24 1AZ .

Fig 18: Identifying Connecting Rod Bearing Cap And Bolts
G09920664Courtesy of BMW OF NORTH AMERICA, INC.

Secure connecting rod bolts (1) with special tool 00 9 120 .

Tightening torque 11 24 1AZ .

Fig 19: Tightening Connecting Rod Bolts Using Special Tool (00 9 120)
G09920665Courtesy of BMW OF NORTH AMERICA, INC.

Assemble engine.

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