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Home >> Subaru >> 2013 >> Forester XT Touring >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 11 (Engine Mechanical (H4DO)) >> Cylinder Block >> Inspection >> Piston Ring

Piston Ring

WARNING: This page is about a different variant/trim than selected.
  1. Make sure the piston ring is not broken or damaged.
  2. Using a cylindrical guide, insert the piston ring and oil ring into the cylinder liner so that they are perpendicular to the cylinder wall, and check the piston ring gap using a thickness gauge. If it is not within the standard, replace the piston ring or oil ring.
    NOTE: Use piston ring with same size as piston when replacing piston ring.

    Piston ring gap: 

    Top ring 

    Standard 

    0.20 - 0.30 mm (0.0079 - 0.0118 in) 

    Second ring 

    Standard 

    0.30 - 0.45 mm (0.0118 - 0.0177 in) 

    Oil ring rail 

    Standard 

    0.20 - 0.50 mm (0.0079 - 0.0197 in) 

    Fig 1: Measuring Piston Ring Gap Using Thickness Gauge
    G08563270Courtesy of SUBARU OF AMERICA, INC.
  3. Fit the piston ring straight into the piston ring groove, then check the clearance between piston ring and piston ring groove with a thickness gauge. If it is not within the standard, replace the piston ring or oil ring.
    NOTE:
    • Before measuring the clearance, clean the piston ring groove and piston ring.
    • Use piston ring with same size as piston when replacing piston ring.

    Clearance between piston ring and piston ring groove: 

    Top ring 

    Standard 

    0.040 - 0.080 mm (0.0016 - 0.0031 in) 

    Second ring 

    Standard 

    0.030 - 0.070 mm (0.0012 - 0.0028 in) 

    Fig 2: Measuring Clearance Between Compression Ring And Piston Using Thickness Gauge
    G08317252Courtesy of SUBARU OF AMERICA, INC.