Piston Ring

WARNING: This page is about a different variant/trim than selected.

Make sure the piston ring is not broken or damaged.
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

0.20 - 0.25 mm (0.0079 - 0.0098 in)

Compression ring (second ring)

Standard

0.25 - 0.35 mm (0.0098 - 0.0138 in)

Oil ring (upper rail and lower rail)

Standard

0.10 - 0.35 mm (0.0039 - 0.0138 in)

Fig 1: Checking Piston Ring Gap Using Thickness Gauge
Courtesy of SUBARU OF AMERICA, INC.
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.
NOTE:
- Measurement should be performed at a temperature of 20°C (68°F).
- 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

0.030 - 0.070 mm (0.0012 - 0.0028 in)

Fig 2: Checking Clearance Between Compression Ring And Piston
Courtesy of SUBARU OF AMERICA, INC.