11 25 671 Replacing piston rings on all pistons (N18)

WARNING: This page is about a different car, the 2016 MINI Cooper Paceman, 2015 MINI Cooper Paceman, 2014 MINI Cooper Paceman, and 2013 MINI Cooper. However, it is still accessible from the selected car via links, so may be relevant.

Special tools required:

11 9 670

Necessary preliminary work:

Remove all PISTONS .

Measuring side 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 Piston Rings Side Clearance

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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 bearing 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

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Installation note:

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

Determine END CLEARANCE with a feeler gauge.

Fig 3: Measuring Piston Rings End Clearance With Feeler Gauge

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Installation note:

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

Fig 4: Identifying Piston Rings With TOP Identification

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Installation note:

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

Plain rectangular compression ring
Lug face ring
Two-part oil scraper ring

Fig 5: Identifying Compression Ring, Taper Face Ring And Two-Part Oil Scraper Ring

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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°.

Fig 6: Identifying Steel Band Rings And Bearing Spring

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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 gudgeon pin boss.

Coat special tool 11 9 670 with sufficient engine oil Risk of damage! to piston rings!

NOTE: See illustration.

Fig 7: Identifying 120° Offset Of Piston Ring Contact Points

Courtesy of BMW OF NORTH AMERICA, INC.

Assemble engine.