11 25 671 Replacing Piston Rings On All Pistons (N51)
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2013 BMW 128i, 2012 BMW 128i, 2011 BMW 128i, 2010 BMW 128i, and 2009 BMW 128i. However, it is still accessible from the selected car via links, so may be relevant.
Necessary preliminary tasks:
- Remove all pistons . See 11 25 530 REMOVING AND INSTALLING/REPLACING ALL PISTONS (N51) .
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.
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.
Put aside piston rings in correct sequence and installation position.
It might not be possible to find the identification on used piston rings.
Installation:
New pistons may only be installed together with new piston rings.
Determine gap with a feeler gauge.
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
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°.
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.