If the brakes are continuously pumped, what should occur?

When brakes are continuously pumped, the expected outcome is that the valves in the air brake system will pop out when the air pressure falls to a critical level, typically around 20-40 PSI. This is a safety feature designed to prevent the brakes from releasing inadvertently when the air pressure becomes too low. The purpose of these valves, or the "safety valves," is to ensure there is sufficient air pressure in the system to maintain proper braking function.

When air pressure drops to this level, the system is signaling that it cannot safely hold the brakes, and thus it initiates a preventative measure to protect against brake failure. Pumping the brakes continually may lead to this condition as air is released from the brake system faster than it can be replenished.

Understanding this mechanism is vital for ensuring safety considerations and recognizing the importance of monitoring air pressure levels in a commercial vehicle's braking system.