Checking the side clearance of the new piston rings

Prerequisite 

Piston cleaned.

• Note the arrangement of the piston rings: 

  Upper piston ring (1):  Plain rectangular compression ring (engraving must point upwards)

  Center piston ring (2):  Taper faced piston ring (engraving must point upwards)

  Oil scraper ring (3):  consisting of 2 piston rings (O1) and (O3) with spring (O2) in the center

  Courtesy of BMW OF NORTH AMERICA, INC.

  Check 

• Use a feeler gauge to check the side clearance of the new upper  piston ring (plain rectangular compression ring)  .
• Determining the correct set of the piston ring (1) (see the applicable BMW Parts Catalog):

  Courtesy of BMW OF NORTH AMERICA, INC.

  Engine	Set of piston rings	Pistons	Side clearance of the upper piston ring
  B38M1 ECE	8 693 017	8 678 931	0.02 - 0.07 mm
  B38M1 ECE	8 693 017	9 494 399	0.04 - 0.08 mm
  B48M1 ECE	8 693 017	8 678 931	0.02 - 0.07 mm
  B48M1 ECE	8 693 017	9 494 399	0.04 - 0.08 mm
  B38M1 CN	8 693 017	8 678 931	0.02 - 0.07 mm
  B38M1 CN	9 847 276	8 681 079	0.035 - 0.085 mm
  B48M1 CN	8 693 017	8 678 931	0.02 - 0.07 mm
  B48M1 CN	9 847 276	8 681 079	0.035 - 0.085 mm
  B48O1 ECE+CN	8 693 017	8 678 934	0.02 - 0.07 mm
  B48T1 ECE+CN	9 846 014	9 488 343	0.03 - 0.07 mm
  B58M1	9 847 276	8 681 079	0.035 - 0.85 mm
  B58O1	9 693 017	8 678 934	0.02-0.07 mm

  Result 

  » The side clearance is outside the tolerance.

  Measure 

  • Replace the piston.
• Note the arrangement of the piston rings: 

  Upper piston ring (1):  Plain rectangular compression ring (engraving must point upwards)

  Center piston ring (2):  Taper faced piston ring (engraving must point upwards)

  Oil scraper ring (3):  consisting of 2 piston rings (O1) and (O3) with spring (O2) in the center.

  Courtesy of BMW OF NORTH AMERICA, INC.

  Check 

• Use a feeler gauge to check the side clearance of the new middle  piston ring (taper faced piston ring  ).
• Determining the correct set of the piston ring (1) (see the applicable BMW Parts Catalog):

  Engine	Set of piston rings	Pistons	Side clearance of the piston ring in the center
  B38M1 ECE	8 693 017	8 678 931	0.03 - 0.07 mm
  B38M1 ECE	8 693 017	9 494 399	0.03 - 0.07 mm
  B48M1 ECE	8 693 017	8 678 931	0.03 - 0.07 mm
  B48M1 ECE	8 693 017	9 494 399	0.03 - 0.07 mm
  B38M1 CN	8 693 017	8 678 931	0.03 - 0.07 mm
  B38M1 CN	9 847 276	8 681 079	0.015 - 0.06 mm
  B48M1 CN	8 693 017	8 678 931	0.03 - 0.07 mm
  B48M1 CN	9 847 276	8 681 079	0.015 - 0.06 mm
  B48O1 ECE+CN	8 693 017	8 678 934	0.03 - 0.07 mm
  B48T1 ECE+CN	9 846 014	9 488 343	0.025 - 0.07 mm
  B58M1	9 847 276	8 681 079	0.015 - 0.06 mm
  B58O1	9 693 017	8 678 934	0.03 - 0.07 mm

  Courtesy of BMW OF NORTH AMERICA, INC.

  Result 

  » The side clearance is outside the tolerance.

  Measure 

  • Replace the piston.