Piston Ring: Service and Repair

11 25 671 - Replacing piston rings on all pistons (S65)





Necessary preliminary tasks:
- Removing all pistons Service and Repair





Remove piston rings with a 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.





Installation:
Piston rings marked with "R" must point to piston crown.

Groove (2), plain compression ring.

Groove (3), stepped ring.
Groove (4), bevel-edged oil control ring.





Piston ring (1), bevel-edged oil control ring.
Piston ring (2), stepped ring.
Piston ring (3), plain compression ring.






Installation:
Piston rings marked with "R" must point to piston crown.

Plain compression ring is marked with (R).

Stepped ring is marked with (R1).





Measure axial play.





Measure end clearance.





Offset the contact points of the piston rings by approx. 120° to each other but do not position above the piston pin boss.

Note:
See picture S85.





Assemble engine.