Piston Ring

1. Make sure the piston ring is not broken or damaged.
2. Using a cylindrical guide, insert the piston 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.
   NOTE:

   • Measurement should be performed at a temperature of 20°C (68°F)  .
   • Use piston ring with same size as piston when replacing piston ring  .

   Piston ring gap: 

   Compression ring (top ring) 

   Standard 

   0.22 - 0.27 mm (0.0087 - 0.0106 in)

   Compression ring (second ring) 

   Standard 

   0.35 - 0.45 mm (0.0138 - 0.0177 in)

   Oil ring (upper rail and lower rail) 

   Standard 

   0.10 - 0.35 mm (0.0039 - 0.0138 in)

   Courtesy of SUBARU OF AMERICA, INC.

3. Fit the compression ring straight into the piston ring groove, then check the clearance between compression ring and piston with a thickness gauge. If it is not within the standard, replace the compression ring.

• Before inspecting the clearance, clean the piston ring groove and compression ring  .
• Use compression ring with same size as piston when replacing compression ring  .

Clearance between compression ring and piston: 

Top ring 

Standard 

0.040 - 0.080 mm (0.0016 - 0.0031 in)

Second ring 

Standard 

0.045 - 0.085 mm (0.0018 - 0.0034 in)

Courtesy of SUBARU OF AMERICA, INC.