Piston Ring: Service and Repair

11 25 671 - Replacing piston rings on all pistons (N73)





Necessary preliminary tasks:
- Remove pistons Service and Repair.





Measuring axial clearance of piston rings in piston ring groove (1 and 2):
Technical Data.

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





Remove piston rings (1 and 2) with piston ring compressing pliers.

Note:
It might not be possible to find the identification on used piston rings.
Put aside piston rings in correct sequence and installation position.
New pistons may only be installed together with new piston rings.





Measure end clearance.





Note:
Picture shows a schematic representation.

Installation Note:
Install piston rings with "TOP" to piston top.

1. Plain compression ring
2. Stepped compression ring "Top"
3. Two-part oil scraper ring.
Offset the contact points of the piston rings by approx. 120° to each other but do not position above the piston pin boss.





Installation Note:
Oil control ring comprises two steel band rings (1) and a support spring (2).
Insert support spring (2) into piston ring groove and then fit steel band rings (1) so that contact points are offset by approx. 120°.