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Home >> Audi >> 2010 >> S4 Automatic DCT >> Repair and Diagnosis >> External Pages >> Different car >> Section 195 (Engine Mechanical (H4DO)) >> Cylinder Block >> Inspection >> Piston Ring

Piston Ring

WARNING: This page is about a different car, the 2012 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.
  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: 

    Standard 

    Top ring 

    0.20 - 0.30 mm (0.0079 - 0.0118 in) 

    Second ring 

    0.30 - 0.45 mm (0.0118 - 0.0177 in) 

    Oil ring rail 

    0.20 - 0.50 mm (0.0079 - 0.0197 in) 

    Fig 1: Checking Piston Ring Gap Using Thickness Gauge
    G07669669Courtesy 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: 

    Standard 

    Top ring 

    0.040 - 0.080 mm (0.0016 - 0.0031 in) 

    Second ring 

    0.030 - 0.070 mm (0.0012 - 0.0028 in) 

    Fig 2: Checking Clearance Between Piston Ring And Piston Ring Groove With Thickness Gauge
    G07669670Courtesy of SUBARU OF AMERICA, INC.