Removing and installing/replacing all pistons (S55 engine)

Special tools required:

00 9 120
11 4 491
11 4 492
11 8 141
11 8 562
11 8 564
11 8 590

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

CAUTION: If pistons, connecting rods and bearing shells are reused, they must be reinstalled in the same place .
Piston and gudgeon pins are paired and must not be fitted individually.
It is not permissible to replace a single piston, all pistons must be always replaced. For further information, see Electronic Parts Catalogue
Make sure that the pistons with same classification are used while replacing the pistons.
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:

Remove ENGINE .
Mount engine on ASSEMBLY STAND .
Remove intake PLENUM .
Remove CYLINDER HEAD .
Remove OIL SUMP .
Remove OIL SUCTION PUMP .
Remove OIL PUMP .

NOTE: In event of heavy oil carbon residue:

Carefully remove oil carbon residue from cylinder wall.

NOTE: Illustration shows N46.

Courtesy of BMW OF NORTH AMERICA, INC.

CAUTION: Do not release screw (1).
OIL SPRAY NOZZLE (2) must not be maladjusted or bent.
If necessary, readjust (risk of damage) .

Courtesy of BMW OF NORTH AMERICA, INC.

Release connecting rod bolts (1).

Tightening torque 11 24 1AZ .

Remove connecting rod bearing cap (2).

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

Courtesy 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.

CAUTION: Risk of damage to oil spray nozzle.

Courtesy 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: Illustration shows N52.

Courtesy 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 gudgeon pin circlip (1), support with special tool 11 4 492 on piston (2).

Lever out gudgeon pin circlip (1) in direction of arrow using special tool 11 4 492.

Courtesy of BMW OF NORTH AMERICA, INC.

CAUTION: 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.

Courtesy of BMW OF NORTH AMERICA, INC.

Measuring 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.

Courtesy 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.

Piston installation clearance.

Total permissible wear tolerance: refer to TECHNICAL DATA .

Installation note:

If necessary, replace piston .

Courtesy of BMW OF NORTH AMERICA, INC.

WARNING: Safety goggles must be worn.

CAUTION: The opening of the gudgeon pin circlip needs to be mounted on the piston in the 6 o'clock position .
Risk of damage!

Courtesy of BMW OF NORTH AMERICA, INC.

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

Bring gudgeon pin circlip (2) into assembly position (1).

WARNING: Safety goggles must be worn.

Slide on special tool 11 8 564 up to the gudgeon pin circlip (1).

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

Courtesy of BMW OF NORTH AMERICA, INC.

WARNING: Safety goggles must be worn.

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, then the gudgeon pin circlip must be driven in using a plastic hammer in direction of arrow.

NOTE: See illustration.

Courtesy of BMW OF NORTH AMERICA, INC.

Gudgeon pin circlip is correctly positioned, if opening (1) points downwards.

Courtesy 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 tabs (1) on special tool 11 8 590 are positioned correctly and check for damage.

Courtesy of BMW OF NORTH AMERICA, INC.

Insert piston with connecting rod in cylinder.

CAUTION: 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.

Courtesy of BMW OF NORTH AMERICA, INC.

CAUTION: Connecting rod and connecting rod bearing cap are marked with pairing letters (1) and must not be mixed up.
Mixing them up or incorrect assembly of the connecting rod bearing cap on the connecting rod will result in engine damage .

Courtesy of BMW OF NORTH AMERICA, INC.

Apply a light coat of oil to crankshaft journals.

Attach connecting rod to crankshaft journal.

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

NOTE: Illustration shows N54.

Courtesy 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 .

Courtesy of BMW OF NORTH AMERICA, INC.

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

Tightening torque 11 24 1AZ .

Courtesy of BMW OF NORTH AMERICA, INC.

Assemble engine.