Piston Assembly Note

WARNING: This page is about a different car, the 2008 Mazda 3. However, it is still accessible from the selected car via links, so may be relevant.

Press the piston into the dust seal opening as shown in the figure.

Fig 1: Identifying Piston And Dust Seal
Courtesy of MAZDA MOTORS CORP.
Insert a piece of wood between the caliper body and the piston, and while supporting the piston by hand, blow compressed air through the brake hose installation hole.
WARNING:
- When blowing compressed air into the caliper body, the piston may pop out and cause injury if not supported at the correct point. Securely support the piston friction surface by hand when blowing compressed air.
  
  Fig 2: Blowing Compressed Air Through Brake Hose Hole
  Courtesy of MAZDA MOTORS CORP.
NOTE:
- By blowing compressed air, the dust seal expands due to air pressure and covers the piston end.
Verify that the dust seal lip covers the piston end as shown in the figure.
Press the piston into the caliper body completely.

Fig 3: Identifying Dust Seal Lip
Courtesy of MAZDA MOTORS CORP.