Instructor
CDL Study Buddy Team
This comprehensive air brake test video covers all seven required checks in one complete tutorial, serving as the definitive resource for CDL candidates preparing for the air brake portion of their skills test.
The video follows the structured sequence that CDL examiners expect, beginning with the initial gauge and warning light check. The instructor explains how to verify that both the primary and secondary air systems show consistent pressure and that all warning indicators illuminate during the bulb check. Understanding your baseline readings is emphasized as a prerequisite for all subsequent tests.
The parking brake check is demonstrated with clear safety protocols. You will learn how to properly engage the parking brake valves (both yellow diamond and red octagonal), place the vehicle in the lowest gear, and gently apply throttle to confirm the brakes hold. The instructor explains the mechanical function of spring brakes and why this test is essential for safety.
The service brake test covers both static and applied checks. From the in-cab perspective, you will learn to apply full service brake pressure, hold for one minute, and monitor for any pressure drop that would indicate a leak in the service brake circuit. The pedal feel assessment is explained in detail — a firm, high pedal indicates proper brake adjustment and no air in the system.
Air pressure build-up is demonstrated with precise timing and an explanation of what affects build-up rate, including engine RPM, compressor condition, and system volume. The governor cut-out and cut-in checks are then performed, with multiple cycles shown to reinforce the expected pressure ranges.
The air loss rate test is demonstrated twice — first with the brakes released, then with the brakes fully applied. The instructor uses a stopwatch and explains exactly how examiners time this test. You will see what acceptable leak rates look like on the gauge and learn to identify patterns that indicate specific types of leaks.
The low air pressure warning test and emergency spring brake activation test conclude the comprehensive check. The instructor explains the interlock between low pressure and spring brake activation, which prevents the vehicle from being driven with insufficient braking capability.
For thorough preparation, pair this comprehensive video with our free CDL practice tests. Consult the FMCSA at https://www.fmcsa.dot.gov/ for official air brake system standards and your state's CDL handbook for state-specific requirements.
