What is an indicator of an air leak in the braking system?

Answer: B — Continuous hissing sound when brakes are applied

A continuous hissing sound when brakes are applied is a clear indicator of an air leak in the braking system. This sound typically signifies that air is escaping from the brake lines or components, which can lead to decreased brake performance and potentially dangerous driving conditions. In a well-functioning brake system, air should not be escaping; therefore, if a hissing sound is present, it is critical to investigate the source of the leak. This can involve inspecting hoses, fittings, and the overall integrity of the braking system to ensure all connections are secure and that there are no damaged components. Understanding this sound can help drivers and maintenance personnel identify issues early, allowing for prompt repairs that are necessary to maintain safety on the road.