11 25 530 Removing and installing/replacing all pistons (N63) - up to 3/2011

WARNING: This page is about a different variant/trim than selected.

Special tools required:

WARNING: Safety goggles must be worn when working on the gudgeon pin circlip.

IMPORTANT: If pistons and connecting rods are reused, they must be reinstalled in the same places.
Pistons and gudgeon pins are matched to each other and can only be replaced as a pair.
Connecting rod and connecting rod bearing cap are cracked.
Identification is effected by means of identical pairing letters on the connecting rod big end.
Mixing up the components will result in engine damage.
Connecting rod bearings must always be replaced.

Necessary preliminary tasks:

Fully remove front axle together with engine.
Remove engine from front axle. See procedure for applicable transmission/drive configuration:
Mount engine on ASSEMBLY STAND .
Remove both cylinder heads. See REMOVING LEFT CYLINDER HEAD and REMOVING RIGHT CYLINDER HEAD .
Remove oil pan. See REMOVING LOWER OIL SUMP SECTION and REMOVING UPPER OIL SUMP SECTION .
Remove OIL PUMP

Unscrew connecting rod bearing cap.

NOTE: Connecting rods and connecting rod bearing caps are denoted with the same pairing letters.
The production dates are always arranged in opposite directions.
Set down connecting rod bearing caps in order.

Fig 1: Identifying Pairing Letters

Courtesy of BMW OF NORTH AMERICA, INC.

NOTE: For installation and dismantling of the connecting rods, it is essential for the crankshaft to be exactly in alignment with the cylinder bore (see dashed line).

Position crankshaft at central bolt.

Insert special tool 11 8 152 into connecting rod.

Screw special tool 11 5 440 into connecting rod with bolt (1).

Remove connecting rod with piston from cylinder head side.

Fig 2: Pressing Out Connecting Rod And Piston Toward Cylinder Head Side

Courtesy of BMW OF NORTH AMERICA, INC.

IMPORTANT: Pistons and gudgeon pins are paired and must not be fitted individually.

Lift out circlip and press out piston pin.

Fig 3: Lifting Out Circlip

Courtesy of BMW OF NORTH AMERICA, INC.

If necessary, replace connecting rods.

NOTE: The connecting rod can also be replaced individually.
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 4: Pressing Gudgeon Pin Through Bush

Courtesy of BMW OF NORTH AMERICA, INC.

Prior to installation, 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.

Measuring point A.

Fig 5: Measuring Piston Installation Clearance

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.

Refer to DIAMETER OF CYLINDER BORE , PISTON INSTALLATION CLEARANCE , and TOTAL PERMISSIBLE WEAR CLEARANCE .

Fig 6: Measuring Cylinder Bore

Courtesy of BMW OF NORTH AMERICA, INC.

IMPORTANT: The connecting rods of cylinder banks 1 to 4 and 5 to 8 are fitted to the pistons differently.

NOTE: The pistons and connecting rods of cylinders 1 to 8 are identical.

Fig 7: Identifying Pistons And Connecting Rods

Courtesy of BMW OF NORTH AMERICA, INC.

Arrow on piston crown (cyl. 1 to 4) points upwards, bolt connection on connecting rod points at an angle to right.

Arrow on piston crown (cyl. 5 to 8) points upwards, screw connection on connecting rod points at an angle to left.

NOTE: For purposes of clarity, pistons are shown removed.

The connecting rods are correctly mounted on the piston when the screw connections on the connecting rods are parallel to each other (see arrow).

Fig 8: Identifying Connecting Rods Mounted On Piston

Courtesy of BMW OF NORTH AMERICA, INC.

Install circlip.

Fig 9: Installing Circlip

Courtesy of BMW OF NORTH AMERICA, INC.

Installation note:

Piston circlip (1) is correctly installed when the opening points upwards.

See Fig 10.

It must still be possible for the gudgeon pin to be moved easily.

Fig 10: Identifying Correct Installation Position Of Piston Circlip

Courtesy of BMW OF NORTH AMERICA, INC.

Insert special tools 11 8 151 and 11 8 152 into connecting rod.

Install CONNECTING ROD BEARING .

Fig 11: Inserting Special Tools Into Connecting Rod

Courtesy of BMW OF NORTH AMERICA, INC.

Lightly coat pistons and piston rings with oil.

Offset the contact points of the piston rings by approx. 120° to each other but do not position above the gudgeon pin boss.

NOTE: Picture shows S85.

Fig 12: Identifying 120° Offset Of Piston Ring Contact Points

Courtesy of BMW OF NORTH AMERICA, INC.

Keep piston rings compressed with special tool 11 7 280 .

Install piston so that arrow points to camshaft drive.

IMPORTANT: Risk of breakage of piston rings.

Press in piston only with finger force (do not knock in!).

Fig 13: Identifying Special Tool 11 7 280

Courtesy of BMW OF NORTH AMERICA, INC.

IMPORTANT: Risk of breakage of piston rings.

Press in piston (1) only with finger force (do not knock in!).

Fig 14: Pressing-In Piston Using Finger Force

Courtesy of BMW OF NORTH AMERICA, INC.

The direction arrow on the piston crown must point to the camshaft drive (direction of travel towards front).

Fig 15: Identifying Piston Crown Direction Arrow

Courtesy of BMW OF NORTH AMERICA, INC.

Attach crankshaft journal to connecting rod.

Remove special tools 11 5 440 and 11 8 152 .

Fig 16: Pressing Out Connecting Rod And Piston Toward Cylinder Head Side

Courtesy of BMW OF NORTH AMERICA, INC.

NOTE: For purposes of clarity, the pairing letters (1) are shown on the removed connecting rod.

IMPORTANT: Connecting rods and connecting rod bearing caps are denoted with the same pairing letters (1), do not mix them up.
Fit bearing cap so that pairing letters match up.

Fig 17: Identifying Connecting Rod Pairing Letters

Courtesy of BMW OF NORTH AMERICA, INC.

Apply light coat of oil to connecting rod bearing shells.

Fit bearing cap so that pairing letters match up.

Install new connecting rod bolts.

Fig 18: Identifying Connecting Rod Bolts

Courtesy of BMW OF NORTH AMERICA, INC.

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

Tightening torque 11 24 1AZ .

Fig 19: Tightening Connecting Rod Bolts

Courtesy of BMW OF NORTH AMERICA, INC.

Assemble engine.