What must occur during the hydraulic system test to ensure the test is valid?

During the hydraulic system test, it is crucial for the pedal height to remain steady. This indicates that the hydraulic system is functioning properly without any leaks or mechanical issues. A steady pedal height demonstrates that the hydraulic pressure is being maintained effectively throughout the braking system, ensuring that all components are sealed and operational.

If the pedal were to sink to the floor or show a decrease in height, it would suggest a possible leak in the hydraulic system or that air has entered the brake lines, compromising the effectiveness of the brakes. A vibrating pedal could indicate issues such as warped brake rotors or problems within the ABS system, which are not indicative of proper hydraulic performance. Therefore, maintaining a steady pedal height is essential for validating the test results.