11 25 671 Replacing Piston Rings On All Pistons (N62)

WARNING: This page does not describe the selected car, but rather 13 other vehicles, including the 2010 BMW 650i, 2009 BMW 650i, 2008 BMW 750i, 2008 BMW 750Li, and 2008 BMW 650i. However, it is still accessible from the selected car via links, so may be relevant.

(piston removed)

Measuring axial clearance of piston rings in piston ring groove (1 and 2):

TECHNICAL DATA .

NOTE:

It is not possible to measure the axial clearance of the oil scraper rings.

Fig 1: Checking Piston Ring Axial Clearance

G04739784

Courtesy of BMW OF NORTH AMERICA, INC.

Remove piston rings (1 and 2) with piston ring compressing pliers.

NOTE:

It might not be possible to find the identification on used piston rings.

Put aside piston rings in correct sequence and installation position.

New pistons may only be installed together with new piston rings.

Fig 2: Removing Piston Rings With Piston Ring Compressing Pliers

G04739785

Courtesy of BMW OF NORTH AMERICA, INC.

MEASURE END CLEARANCE .

Fig 3: Checking End Clearance

G04739786

Courtesy of BMW OF NORTH AMERICA, INC.

NOTE:

Picture shows a schematic representation.

Installation:

Install piston rings with "TOP" to piston top.

Plain compression ring
Stepped compression ring "Top"
Steel band ring with support spring

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

Fig 4: Identifying Piston Rings Position

G04739787

Courtesy of BMW OF NORTH AMERICA, INC.

Installation:

Oil control ring comprises two steel band rings (1) and a support spring (2).

Insert support spring (2) into piston ring groove.

CAUTION:

Incorrect installation possible.

Contact points of support spring (2) slip very easily over each other when fitted.

Contact points must be positioned exactly on each other.

If the contact points overlap, the oil scraper ring will be damaged when the piston is installed.

Fig 5: Identifying Support Spring

G04739788

Courtesy of BMW OF NORTH AMERICA, INC.

Then fit steel band rings (1) so that contact joints are offset approx. 120°.