Which situation indicates that a vehicle's brake system is functioning improperly?

The indication that a vehicle's brake system is functioning improperly is when the brakes make noise when applied. Unusual sounds such as squealing, grinding, or clunking when the brakes are engaged typically suggest that there may be a problem with the brake system. These sounds could indicate worn brake pads, a lack of lubrication, or issues with the brake rotors. It's essential for the safety and functionality of the vehicle that any braking noise is investigated and addressed promptly.

In contrast, when the brake fluid is clear, it generally means that the fluid is clean and uncontaminated, which is a positive sign for the brake system. A red brake warning lamp being off indicates that there are no malfunctions detected in the brake system at that moment. Finally, when brakes meet the required stopping distances, it signifies that they are functioning effectively in delivering the necessary stopping power. Thus, the presence of noise during braking serves as a clear signal of potential issues requiring attention.