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

WARNING: This page is about a different car, the 2010 BMW 135i, 2009 BMW 135i, and 2008 BMW 135i. 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.

See ENGINE - TECHNICAL DATA .

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

Fig 2: Removing Compression 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. See ENGINE - TECHNICAL DATA .

Fig 3: Measuring Piston Gap Using Feeler Gauge

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 Piston Rings
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 Steel Band Rings And Support Spring

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 Fig 6 N52.

Fig 6: Off Setting Of Piston Rings Contact Points

Courtesy of BMW OF NORTH AMERICA, INC.

Assemble engine.