Which of the following is a sign that the brake system may be experiencing a leak?

The indication that the brake system may be experiencing a leak is associated with reduced braking efficiency. This occurs because a leak in the brake system can lead to a loss of air pressure, which is crucial for the operation of air brakes. When air pressure decreases, the force applied to the brake components is diminished, resulting in less effective braking action. Drivers may find that their vehicle takes longer to stop or requires more effort on the brake pedal to achieve the desired slowing down or stopping.

Other signs, while they may suggest a problem with the vehicle, do not specifically point to a leak in the brake system. A sudden increase in vehicle speed could indicate a variety of issues, such as driver error or acceleration malfunctions, rather than a braking issue. Increased fuel consumption typically relates more to engine performance and driving habits rather than the brake system directly. Strange noises while braking may indicate worn brake pads or other mechanical issues but do not specifically indicate a leak in the air brake system. Thus, reduced braking efficiency is the most direct and relevant sign of a potential brake system leak.