When applying moderate pressure to the brake pedal of a HydroBoost system after depleting the fluid reserve, what should happen if the system operates properly?

• A. The pedal should remain still.
• B. The pedal should rise immediately.
• C. The pedal should move downward before rising.
• D. The pedal should feel disconnected.

Answer: (C)

In a HydroBoost system, when moderate pressure is applied to the brake pedal after the fluid reserve has been depleted, the correct behavior of the system will see the pedal moving downward before rising. This occurs because the HydroBoost uses hydraulic pressure from the power steering system to assist in braking. With depleting the fluid reserve, the initial application of pressure causes the brake system to momentarily dip as it utilizes the remaining hydraulic assistance and compensates for the lack of brake fluid.

Once the initial downward movement occurs, the system engages the hydraulic pressure effectively and allows the pedal to rise as the brakes begin to engage. This is indicative of a properly functioning HydroBoost system, as it demonstrates the pedal's response to hydraulic assistance despite the lower fluid level.

The other options do not accurately reflect the expected behavior of the system under these conditions, as a stationary pedal, immediate rising without initial movement, or a "disconnected" feeling would suggest a malfunction or failure in the system's hydraulic operation. Thus, the described action of the pedal moving downward and then rising is the correct and expected response for a well-functioning HydroBoost brake system under the given circumstances.