What Are the 7 Steps of an Air Brake Check?

The seven steps are: 1) Check compressor governor cut-out and cut-in, 2) Static leakage test, 3) Applied leakage test, 4) Low-air warning activation, 5) Spring brake “pop-out,” 6) Air pressure build-up rate, and 7) Parking and service brake checks. These steps form the standard U.S. CDL air brake check used in pre-trip inspections for vehicles with air brake systems.

What the “seven-step” air brake check is and why it matters

Used nationwide in commercial driver licensing, the seven-step air brake check verifies that a heavy vehicle’s compressed-air braking system is functioning safely and within legal thresholds. Examiners and safety managers look for specific pressures and time limits—typically: compressor cut-out at about 120–140 psi, cut-in at or above 100 psi; leakage limits of 2–3–4 psi depending on configuration; a low-air warning between 55–75 psi; spring brake engagement between 20–45 psi; and pressure build-up from 85 to 100 psi within 45 seconds on dual systems. Exact criteria can vary slightly by state manual and manufacturer, but the framework is consistent and current across U.S. CDL programs.

The 7 steps, explained

Perform these checks on level ground with wheels chocked. Follow safe procedures: transmission neutral, parking brakes as instructed, and key-on/engine-off states where specified. Announce each step and the expected results if you’re taking a CDL exam.

1. 
   

   Check air compressor governor cut-out and cut-in

   Build system pressure until the governor “cuts out” (typically 120–140 psi), indicated by the compressor unloading and the air dryer purging on many vehicles. Then fan the brakes to drop pressure until the governor “cuts in” (generally at or above 100 psi), indicated by the compressor loading. Both points should occur within manufacturer/state-specified ranges.

2. 
   

   Static leakage test

   With engine off and key on, release the parking brakes so the system is charged. After the initial needle settle, time one minute without touching the brake pedal. Pressure loss should not exceed 2 psi in one minute for single vehicles or 3 psi for tractor-trailer combinations.

3. 
   

   Applied leakage test

   Apply and hold full foot brake pressure for one minute with parking brakes released. Pressure loss should not exceed 3 psi in one minute for single vehicles or 4 psi for combinations. Excess loss suggests leaks at chambers, lines, valves, or fittings.

4. 
   

   Low-air warning device

   Fan the brakes to drop system pressure. The low-air warning (light, buzzer, or message) must activate between 55–75 psi. A late or missing warning indicates a hazardous fault.

5. 
   

   Spring brake (parking brake) “pop-out”

   Continue fanning. The parking brake control(s) should pop out automatically as spring brakes engage, typically between 20–45 psi. Failure to pop out within range is an out-of-service condition.

6. 
   

   Air pressure build-up rate

   Restart the engine. At fast idle as permitted, verify pressure builds from 85 to 100 psi within 45 seconds on dual air systems (commonly tested on a tractor). Slow build indicates compressor, governor, dryer, or restriction issues.

7. 
   

   Parking and service brake checks

   With safe clearance and chocks managed appropriately, perform a tug test to confirm the parking brake holds. Then move forward about 5 mph and apply the service brakes to check for proper stopping, no pull to one side, and no unusual delay or pedal feel.

Together, these steps verify the system’s ability to hold pressure, warn of danger, auto-apply spring brakes at low pressure, rebuild air promptly, and stop the vehicle as intended—core criteria for safe operation and CDL compliance.

Key numbers at a glance

The following thresholds are commonly used across U.S. CDL testing standards and manufacturer guidance. Always verify your state manual and your vehicle’s specifications.

• Governor cut-out: about 120–140 psi; cut-in: at or above 100 psi
• Static leakage: ≤2 psi in 1 minute (single); ≤3 psi (combination)
• Applied leakage: ≤3 psi in 1 minute (single); ≤4 psi (combination)
• Low-air warning: activates between 55–75 psi
• Spring brake pop-out: occurs between 20–45 psi
• Build-up rate: 85 to 100 psi in ≤45 seconds (dual systems)
• Service/parking checks: no vehicle pull or delay; parking brake holds in tug test

These figures are designed to catch early signs of leaks, weak compressors, or faulty valves before they become on-road failures.

Common mistakes and pro tips

Drivers often lose points on exams or miss real defects due to avoidable missteps. Use these reminders to tighten your routine.

• Not chocking wheels before releasing parking brakes
• Skipping key-on/engine-off states when required
• Failing to time a full minute on leakage tests
• Using single-vehicle limits on a combination (or vice versa)
• Idling too high during build-up checks beyond recommended fast idle
• Not stating pass/fail and readings aloud during a CDL test
• Ignoring audible leaks or slow gauges that hint at deeper issues

Practicing the exact script and timing helps you pass exams and uncover real defects that affect stopping performance and legal compliance.

Safety and legal notes

While the seven-step framework is consistent across the U.S., specific pressures and procedures can vary slightly by state CDL manual and vehicle OEM. Always consult your current state CDL guide and your vehicle’s service documentation. As of 2025, the ranges cited here align with widely adopted state standards and FMCSA-aligned training curricula.

Summary

The seven-step air brake check confirms the system’s integrity from compressor control to emergency spring-brake function and real-world stopping. Know the expected PSI ranges and timings, follow safe states (key on/engine off versus running), and document pass/fail results. Done correctly, this routine keeps you compliant—and, more importantly, safe.

What is the 7 in a vehicle equipped with air brakes the brake pedal?

7 – The Brake Pedal. You engage the brakes by pushing down the brake pedal (It is also called a foot valve or treadle valve). Pushing the pedal down harder applies more air pressure. Letting up on the brake pedal reduces the air pressure and releases the brakes.

How do air brakes work step by step?

The air from the valves is delivered to the brake chambers. The chambers move the pushrod to push on the slack adjusters. The adjusters transfer pushrod force into cam rotational force. The cam rotates, causing the rollers to rise and force the shoes against the drum.

What are the most common CDL air brake test mistakes?

Common Mistakes to Avoid

• Confusing service brakes with emergency or parking brakes.
• Failing to understand the importance of air pressure levels.
• Overlooking the need for regular inspection and maintenance.
• Not practicing the air brake system check before the skills test.

What is the 7 step air brake test?

The “7 step air brake test,” also known as the in-cab air brake checks, evaluates the vehicle’s air brake system’s functionality by testing air pressure buildup, air leakage, the low air pressure warning system, and the spring brakes’ engagement and release, ensuring the driver’s safety by confirming the system operates as designed, according to Schneider Jobs and DOT Mobile Express. 
The 7 Steps

1. Governor Cut-In/Cut-Out: Opens in new tabWith the engine off, but the ignition on, the air pressure should build up from a low point. When the compressor cuts in and then cuts out (stops pumping), the gauges should show the appropriate cut-in and cut-out pressure range. 
2. Test Air Leakage Rate: Opens in new tabWith the ignition off, the air pressure should remain constant. If it drops more than a specified amount (e.g., 3 psi) in one minute, there’s an air leak. 
3. Test Low-Pressure Warning: Opens in new tabPress the brake pedal and pump the brakes to lower the air pressure. The low-air warning buzzer and/or light should activate at approximately 60 PSI. 
4. Test Spring Brakes (Parking Brake Application): Opens in new tabContinue pumping the brakes until the spring brakes automatically apply at around 20-40 PSI, indicating that the emergency/parking brakes are functioning correctly. 
5. Test Air Pressure Rebuild Rate: Opens in new tabStart the engine and observe the time it takes for the air pressure to rise from a specific low point (e.g., 85 PSI) to a higher point (e.g., 100 PSI), which should take less than a given time (e.g., two minutes). 
6. Test Parking Brake Hold: Opens in new tabWith the spring brakes engaged, put the vehicle in gear and gently try to pull ahead. The vehicle should not move, proving the parking brakes are holding. 
7. Test Service Brake Hold: Opens in new tabApply the foot brake and gently try to pull ahead. The vehicle should not move, ensuring the service brakes are holding effectively.