What is the acceptable leakage at the governor exhaust valve?

The acceptable leakage at the governor exhaust valve is indicated by a limit of a 3-inch soap bubble forming every three seconds. This standard reflects the operational efficiency and integrity required for air brake systems in school buses. Excessive leakage can compromise the air system's performance, leading to inadequate brake function, which is critical for safety.

A 3-inch soap bubble every three seconds represents a reasonable threshold for leakage in relation to the design and performance specifications of these systems. Acceptance levels for leakage may vary, but manufacturers typically set these standards based on the necessary balance between performance and safety, ensuring that the braking system remains effective under various load conditions.

Lower limits, such as a 1-inch or a 2-inch bubble, would indicate lower tolerances for leakage, but they are not the accepted standards for the governor exhaust valve, making choice C the accurate representation of acceptable leakage.