What could happen if the brake pedal sinks when testing hydraulic brakes?

When testing hydraulic brakes, if the brake pedal sinks, it suggests that there may be a leak in the brake system or potential brake failure. This sinking sensation can indicate that the hydraulic pressure is not being maintained properly, which might be due to a leak in the brake lines, a malfunctioning master cylinder, or air in the brake lines. Such issues can compromise the vehicle's braking ability, making the system less effective or unsafe for operation. Therefore, recognizing that a sinking brake pedal is a warning sign necessitates immediate inspection and repair to ensure the safety and functionality of the braking system.