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Home >> Subaru >> 2005 >> Outback R VDC Limited >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 17 (Engine Mechanical (H4DOTC)) >> Cylinder Block >> Inspection >> Piston Ring

Piston Ring

WARNING: This page is about a different variant/trim than selected.
  1. If the piston ring is broken, damaged or worn, or if its tension is insufficient, or when the piston is replaced, replace the piston ring with a new one of the same size as the piston.
    CAUTION:
    • Marks are displayed on the end of top and second rings. When installing the rings to the piston, face those marks upward.
    • Oil ring consists of the upper rail, expander and lower rail. When installing on piston, be careful of each rail's direction.
      Fig 1: Identifying Piston Ring
      G03829724Courtesy of SUBARU OF AMERICA, INC.
  2. Squarely place the piston ring and oil ring in cylinder, and measure the piston ring gap with a thickness gauge.
    PISTON RING GAP SPECIFICATION

    Standard mm (in)
    Piston ring gap Top ring 0.20 - 0.25 (0.0079 - 0.0098)
    Second ring 0.37 - 0.52 (0.015 - 0.020)
    Oil ring rail 0.20 - 0.50 (0.0079 - 0.0197)
    Fig 2: Measuring Piston Ring Gap With Thickness Gauge
    G03829725Courtesy of SUBARU OF AMERICA, INC.
  3. Measure the clearance between piston ring and piston ring groove with a thickness gauge.
    NOTE: Before measuring the clearance, clean the piston ring groove and piston ring.
    CLEARANCE BETWEEN PISTON RING AND PISTON RING GROOVE

    Standard mm (in)
    Clearance between piston ring and piston ring groove Top ring 0.040 - 0.080 (0.0016 - 0.0031)
    Second ring 0.030 - 0.070 (0.0012 - 0.0028)
    Fig 3: Measuring Clearance Between Piston Ring And Piston Ring Groove
    G03829726Courtesy of SUBARU OF AMERICA, INC.
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