Piston Ring: Service and Repair

11 25 671 Replacing piston rings on all pistons (M57T2-SCR)





Installation Note:
^ Removing piston





Measure axial play.

Refer to Technical Data.

Remove piston rings with piston ring 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.





Measure end clearance with a feeler gauge.





Installation Note:
Install piston rings with "TOP" to piston crown.
1. Plain rectangular compression ring
2. Piston ring
3. Beveled roof ring with spiral expander

Arrange piston ring contact points with offset of approx. 120° to one another, but not over gudgeon pin boss.





Note:
Oil scraper ring comprises two steel band rings (1) and a bearing spring (2).

Installation Note:
Insert bearing 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 gudgeon pin boss.

Illustration shows N52





Assemble engine.