Piston And Piston Pin

WARNING: This page is about a different car, the 2006 Subaru Outback and 2006 Subaru Legacy. However, it is still accessible from the selected car via links, so may be relevant.

Check the pistons and piston pins for damage, cracks and wear, and the piston ring grooves for wear and damage. Replace if faulty.
Measure the piston-to-cylinder clearance at each cylinder. < Ref. to CYLINDER AND PISTON , INSPECTION, Cylinder Block. > If any of the clearances is not within the standard value, replace the piston and bore the cylinder to enable use of an oversized piston.
Make sure that the piston pin can be inserted into the piston pin hole with a thumb at 20°C (68°F). Replace if faulty.
Clearance between piston hole and piston pin:

Standard:

0.004 - 0.008 mm (0.0002 - 0.0003 in)

Fig 1: Measuring Inside Diameter Of Piston
Courtesy of SUBARU OF AMERICA, INC.

Fig 2: Measuring Outer Diameter Of Piston Pin
Courtesy of SUBARU OF AMERICA, INC.
Check the snap ring installation groove (A) on the piston for burr. If necessary, remove burr from the groove so that the piston pin can lightly move.

Fig 3: Identifying Circlip Installation Groove On Piston
Courtesy of SUBARU OF AMERICA, INC.
Check the piston pin snap ring for distortion, cracks and wear.