11 25 530 Removing And Installing/Replacing All Pistons (N73)

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2006 BMW 760i, 2006 BMW 760Li, 2005 BMW 760i, 2005 BMW 760Li, and 2004 BMW 760i. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

For Special Tool identification, see ENGINE- SPECIAL TOOLS and MAINTENANCE AND GENERAL INFORMATION - SPECIAL TOOLS .

Special Tools Required:

00 9 120
11 7 280
11 8 151
11 8 152

Necessary Preliminary Tasks:

Remove engine. Refer to 11 00 050 REMOVING AND INSTALLING ENGINE (N73) .
Remove left cylinder head. Refer to 11 12 105 REMOVING AND INSTALLING LEFT CYLINDER HEAD (N73) .
Remove right cylinder head. Refer to 11 12 106 REMOVING AND INSTALLING RIGHT CYLINDER HEAD (N73) .
Remove oil pump. Refer to 11 41 000 REMOVING AND INSTALLING/REPLACING OIL PUMP (N73) .
Remove upper oil sump. Refer to 11 13 010 REMOVING AND INSTALLING/REPLACING OIL SUMP TOP SECTION (N73) .

IMPORTANT: Re-install piston, connecting rod and bearing shells back in the same position and in the same installation location. Conrods and conrod bearing caps are denoted with the same pairing letters. Do not mix them up as this will cause engine damage .

Unscrew conrod bearing cover.

Set down conrod bearing caps in order.

NOTE: All conrods are cracked.

Do not mix up conrods and conrod bearing caps, observe pairing letters.

Fig 1: Removing Conrod Bearing Cover

Courtesy of BMW OF NORTH AMERICA, INC.

Fit special tools 11 8 151 and 11 8 152.

Remove conrod with piston from cylinder head side.

IMPORTANT: Do not damage cylinder wall when pulling out conrod with piston.

Fig 2: Removing Conrod With Piston From Cylinder Head Side

Courtesy of BMW OF NORTH AMERICA, INC.

When removing and installing pistons with conrods, make sure piston cooling spray nozzles (1) are not bent.

Risk Of Damage.

Fig 3: Locating Piston Cooling Spray Nozzles

Courtesy of BMW OF NORTH AMERICA, INC.

Lift out retaining ring and press out piston pin.

IMPORTANT: Piston and piston pins are paired and must not be fitted individually.

Fig 4: Removing Retaining Ring

Courtesy of BMW OF NORTH AMERICA, INC.

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

Installation:

The conrods can also be replaced individually.

Fig 5: Identifying Connecting Rod With Piston Pin

Courtesy of BMW OF NORTH AMERICA, INC.

Prior to installation, measure piston installation clearance: Measure piston diameter with micrometer at measuring point A from bottom edge of piston and offset at 90° to the axis of the piston pin.

Measuring point A.

Fig 6: Measuring Piston Diameter

Courtesy of BMW OF NORTH AMERICA, INC.

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

Diameter of cylinder bore.

Piston installation clearance.

Total permissible wear tolerance.

Fig 7: Measuring Cylinder Bore Diameter

Courtesy of BMW OF NORTH AMERICA, INC.

Due to the design of the piston head and the piston pin offset, the pistons are constructed specifically for each cylinder bank and must not be mixed up.

Important!

Risk Of Damage.

Fig 8: Identifying Piston Head And Piston Pin Offset

Courtesy of BMW OF NORTH AMERICA, INC.

Cylinder Bank 1 To 6.

Fit conrod with piston pin to piston in such a way that arrow on piston points to front and flat end of conrod points to rear.

IMPORTANT: Conrods for cylinders 1 to 6 and 7 to 12 must be fitted differently to the pistons.

Fig 9: Identifying Connecting Rod With Piston (Cylinder Bank 1 To 6)

Courtesy of BMW OF NORTH AMERICA, INC.

Cylinder Bank 7 To 12.

Fit conrod with piston pin to piston in such a way that arrow on piston points to front and flat end of conrod points to front. Install conrod bearing.

Fig 10: Identifying Connecting Rod With Piston (Cylinder Bank 7 To 12)

Courtesy of BMW OF NORTH AMERICA, INC.

Install retaining ring.

Fig 11: Installing Retaining Ring

Courtesy of BMW OF NORTH AMERICA, INC.

Insert special tools 11 8 151 and 11 8 152 in conrod.

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 piston boss.

Press together piston rings using special tool 11 7 280.

IMPORTANT: Danger Of Piston Ring Failure.

Fig 12: Compressing Rings Using Special Tool

Courtesy of BMW OF NORTH AMERICA, INC.

Keep piston rings pressed with special tool 11 7 280.

Install pistons with arrows pointing towards camshaft drive.

Fig 13: Installing Piston With Special Tool

Courtesy of BMW OF NORTH AMERICA, INC.

IMPORTANT: Danger Of Piston Ring Failure. Only press pistons into place with finger force - do not knock in!

Fit conrod with special tool 11 8 151 and 11 8 152 on crank pin.

Remove special tools 11 8 151 and 11 8 152.

Fig 14: Installing Conrod With Special Tools On Crank Pin

Courtesy of BMW OF NORTH AMERICA, INC.

IMPORTANT: Conrods and conrod bearing caps are denoted with the same pairing letters (1), do not mix them up.

For purposes of clarity, the pairing letters (1) are shown on the removed conrod.

Fig 15: Identifying Conrods And Conrod Bearing Caps Pairing Letters

Courtesy of BMW OF NORTH AMERICA, INC.

Apply light coat of oil to connecting-rod bearing shells.

NOTE: All conrods are cracked. Do not mix up conrods and conrod bearing caps.

IMPORTANT: During installation, make sure conrod bearing caps are correctly seated. Risk of damage.

Install new conrod bolts.

Fig 16: Installing Conrod Bearing Caps

Courtesy of BMW OF NORTH AMERICA, INC.

Tighten down conrod bolts with special tool 00 9 120.

Installation:

Tightening torque, refer to 11 24 1AZ in ENGINE - TIGHTENING TORQUES .

Fig 17: Tightening Conrod Bolts With Torque Angle Measuring Dial

Courtesy of BMW OF NORTH AMERICA, INC.

Assemble engine in reverse sequence to its disassembly.

Installation:

Lubricate all crankshaft bearing positions with engine oil.

NOTE: The pistons are available in two oversizes for subsequent treatment of the cylinders.