11 25 671 Replacing piston rings on all pistons (N52)

WARNING: This page does not describe the selected car, but rather 16 other vehicles, including the 2008 BMW Z4, 2007 BMW Z4, 2007 BMW 530xi, 2007 BMW 530i, and 2007 BMW 525xi. 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: 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: Identifying Compression Ring With Piston Ring Pliers

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: Checking Piston Ring Gap With 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 Components And Position
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 Piston Support Spring And 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 Fig 6.

Fig 6: Identifying Offset Contact Points Of Piston Rings

Courtesy of BMW OF NORTH AMERICA, INC.

Assemble engine.