Impreza L Sedan F4-2.2L SOHC (1997)
6. Brake booster with no vacuum.
When the brake pedal is depressed while constant- and variable-pressure chambers are held at atmospheric pressure, the operating rod moves to
the left. This moves the plunger valve which in turn pushes the hub via the key.
The reaction disc (which is built into the hub) then moves the master cylinder piston via the push rod. At this point a boosting force does not occur,
but oil pressure is produced by movement of the master cylinder piston. As a result, the system serves as a hydraulic brake.
