11 25 671 Replacing piston rings on all pistons

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2010 BMW 535xi, 2010 BMW 535i, 2009 BMW 535xi, 2009 BMW 535i, and 2008 BMW 535xi. 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

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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 And Stepped Ring Upwards With Piston Ring Pliers

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Installation note:

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

Determine gap with a feeler gauge. See ENGINE BLOCK, CYLINDER CRANKCASE N54 B30 and PISTONS WITH RINGS AND PINS N54 B30 .

Fig 3: Checking Piston Gap Using Feeler Gauge

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NOTE: Schematic representation of piston rings.

Installation note:

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

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

Fig 4: Schematic Representation Of 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 note:

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 And Steel Band Rings

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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 illustration N52.

Fig 6: Identifying Piston Rings Offset Contact Points

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Assemble engine.