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

WARNING: This page is about a different car, the 2005 BMW 645Ci and 2004 BMW 645Ci. 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):

Refer to ENGINE - TECHNICAL DATA - 645CI

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

Fig 1: Measuring Axial Clearance Of Piston Rings In Piston Ring Groove

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

Fig 2: Removing Piston Rings With Piston Ring Compressing Pliers

Courtesy of BMW OF NORTH AMERICA, INC.

Put aside piston rings in correct sequence and installation position.

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

Measure end clearance. Refer to ENGINE - TECHNICAL DATA - 645CI

Fig 3: Measuring End Clearance

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.

Fig 4: Identifying Piston Rings

Courtesy of BMW OF NORTH AMERICA, INC.

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

Installation:

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

Fig 5: Identifying Oil Control Ring Components

Courtesy of BMW OF NORTH AMERICA, INC.

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.

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