WARNING: This page is about a different car, the 2005 Mazda MX-5 Miata. However, it is still accessible from the selected car via links, so may be relevant.
Push the primary piston component in fully.
Fig 1: Pushing Primary Piston Component In Fully
Courtesy of MAZDA MOTORS CORP.
Install and tighten a new O-ring and the stop screw.
Push and release the piston to verify that it is held by the stop screw.