11 25 671 Replacing Piston Rings On All Pistons (N54)

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2010 BMW 335xi, 2010 BMW 335i, 2009 BMW 335xi, 2009 BMW 335i, and 2008 BMW 335xi. However, it is still accessible from the selected car via links, so may be relevant.

Necessary preliminary tasks:

Remove all pistons.

Measuring axial clearance of piston rings in piston ring groove.

Technical Data.

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

Fig 1: Identifying Clearance Of Piston Rings In Piston Ring Groove

Courtesy of BMW OF NORTH AMERICA, INC.

Remove compression ring and stepped ring upwards with piston ring pliers.

Oil scraper ring comprises two steel band rings and a support spring.

NOTE:

Oil scraper ring cannot be removed with piston ring pliers.

Put aside piston rings in correct sequence and installation position.

Fig 2: Removing Piston Ring

Courtesy of BMW OF NORTH AMERICA, INC.

Installation:

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

Determine gap with a feeler gauge.

Fig 3: Identifying Piston Rings Gap

Courtesy of BMW OF NORTH AMERICA, INC.

NOTE: Schematic representation of piston rings.

Installation:

Piston rings with "TOP" identification must point to piston crown.

Plain compression ring
Stepped compression ring "Top"
Two-part oil scraper ring

Fig 4: Identifying Plain Compression Ring, Compression Ring & Oil Scraper Ring
Courtesy of BMW OF NORTH AMERICA, INC.

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

Installation:

Insert support spring (2) into piston ring groove and then fit steel band rings (1) so that contact points are offset by approx. 120°.

Fig 5: Identifying Support Spring & Steel Band Rings

Courtesy of BMW OF NORTH AMERICA, INC.

Offset the contact points (1) of the piston rings by approx. 120° to each other but do not position above the piston pin boss.

NOTE: See N52.

Fig 6: Identifying Contact Points Of Piston Rings

Courtesy of BMW OF NORTH AMERICA, INC.

Assemble engine.