What is the 7-step air brake test?

The 7-step air brake test is a standardized, in-cab procedure used in commercial driver training and CDL skills exams to verify that an air brake system is safe and functioning. In practice, it covers pressure build-up and governor operation, air loss (leak) checks, the low-air warning, spring brake “pop-out,” rate-of-build, and final service/parking brake checks. While the exact sequence and wording can vary by state or examiner, the core safety checks and pressure thresholds are widely consistent across North America.

How the 7-step air brake test is performed

The following sequence reflects the traditional seven-part approach commonly taught in U.S. CDL programs. Perform the test on level ground with wheels chocked as needed, follow your jurisdiction’s manual for any local variations, and narrate each step clearly during an exam.

1. Build to governor cut-out (system fully charged). Start the engine, set the parking brake, and allow pressure to build until the governor cuts out (typically 120–140 psi). You’ll note the cut-out when the gauges stop rising and/or you hear the air dryer purge.
2. Static air loss test (engine off, key on). Turn the engine off, key on, release the parking brake to charge the system. After the initial needle drop stabilizes, observe for one minute without touching the brake pedal. Loss should not exceed 2 psi per minute for a single vehicle or 3 psi per minute for a combination.
3. Applied air loss test. With the parking brake still released, fully apply and hold the service brake for one minute. Loss should not exceed 3 psi per minute for a single vehicle or 4 psi per minute for a combination.
4. Low-air warning device check. Fan (pump) the brake pedal to reduce system pressure. The low-air warning light and/or buzzer must activate by about 55–75 psi (at or above 55 psi).
5. Spring brake “pop-out” (emergency) test. Continue fanning the brakes until the parking brake control valve “pops out” and the spring brakes set automatically, typically between 20–45 psi.
6. Governor cut-in and rate-of-build. Restart the engine and set a fast idle. After pressure drops below cut-in, verify the governor cuts in (needles begin rising) around 90–100 psi. Then time the rise from 85 to 100 psi: it must occur within 45 seconds for both single and combination vehicles (consult your manual for any stricter local limit).
7. Service and parking brake checks (rolling test). With full pressure restored, perform a gentle tug test against the set parking brake to confirm it holds. Then release the parking brake, move forward at about 5 mph, and apply the service brake firmly; the vehicle should stop straight without pulling or lag. For combinations, many jurisdictions also require tug tests of the trailer parking brake and a tractor protection/air supply check per the local CDL manual.

These seven actions collectively verify the system’s ability to hold pressure, warn of danger, apply emergency spring brakes automatically, rebuild air quickly, and stop the vehicle safely under control.

Typical pressure thresholds and limits to remember

While you must always follow your state or province’s CDL handbook, these figures are widely accepted across North America and align with AAMVA-based testing practices.

• Governor cut-out: about 120–140 psi
• Governor cut-in: commonly around 90–100 psi
• Low-air warning activation: at or above 55 psi (often within 55–75 psi)
• Spring brake pop-out: typically 20–45 psi
• Static leak: max 2 psi/min (single) or 3 psi/min (combination)
• Applied leak: max 3 psi/min (single) or 4 psi/min (combination)
• Rate of build: 85 to 100 psi in 45 seconds or less

If your local manual lists different numbers or requires additional demonstrations (for example, separate tractor and trailer brake tug tests), use those figures and steps during training and exams.

Why this test matters—and common exam tips

Air brake failures are high-risk events; this test confirms the system can alert drivers to danger, apply emergency brakes automatically, and rebuild pressure fast enough for safe operation. Examiners also evaluate how clearly and accurately you call out what you are doing and what you observe.

• Speak the numbers. Say what you expect and what you see (for example, “Governor cut-out at 125 psi”).
• Stabilize before timing. Let needles settle before starting one-minute leak checks.
• Mind the sequence. Do not skip releasing the parking brake before leak checks.
• Safety first. Chock wheels when appropriate and keep the vehicle controlled at all times.
• Know your vehicle. Some buses or specialty trucks have manufacturer-specific thresholds—follow the stricter requirement.

Clear narration, careful timing, and adherence to thresholds demonstrate both system knowledge and safe operating habits—key for passing and for daily driving.

State differences and the modernized CDL skills test

Many states still use the traditional 7-step format. Others have adopted the Modernized CDL Skills Test model, which may group or label checks differently but still requires you to verify air leakage limits, low-air warning, spring brake operation, governor cut-in/out, and adequate pressure build. Always practice using the exact script and order in your jurisdiction’s current CDL manual.

Summary

The 7-step air brake test is the in-cab safety check used in CDL training and exams to confirm air system integrity: build to cut-out, perform static and applied leak checks, verify the low-air warning and spring brake pop-out, confirm governor cut-in and pressure build rate, and finish with service/parking brake checks. Follow your local manual for the precise sequence and thresholds, narrate clearly, and time each step carefully to meet exam standards and ensure real-world safety.

How to do a proper air brake test?

To test your air brakes, first build air pressure in the system, then turn the engine off and perform an air leak test by watching the gauges for a 1-minute period while holding the brake pedal down. Next, fan the brakes to activate the low-air pressure warning light and buzzer, and finally, continue to fan the brakes until the tractor protection and parking brake valves pop out, indicating they function correctly. 
1. Build Air Pressure and Governor Cut-Out Test 

• Start the engine Opens in new taband allow the air pressure to build to the normal operating range (often 120-140 PSI), or as specified by the manufacturer. 
• Release the parking brake Opens in new taband listen for the air compressor to shut off, which indicates the governor cut-out pressure has been reached. 

2. Air Leak Test (Holding the Brake)

• Turn the engine OFF: and the ignition to the ON position (without starting the engine). 
• Press and hold the foot brake: to apply the service brakes. 
• Watch the air pressure gauges: and time for 60 seconds. The pressure should not drop by more than 4 PSI in this minute, indicating a lack of leaks. 

3. Low Air Pressure Warning Light and Buzzer Test 

• Pump the brake pedal: to drain air from the system. 
• Listen and watch: for the low air pressure warning light and buzzer to come on. These should activate at or before 60 PSI. 

4. Valve Deployment Test (Tractor and Parking Brake Valves) 

• Continue pumping the brake pedal .
• Observe the gauges: as you continue to drain air. The red trailer supply valve and the yellow service brake valve (tractor protection and parking brake valves) should pop out automatically between 20 and 40 PSI.

5. Check and Rebuild Pressure 

• Start the engine: again.
• Allow the air pressure: to build back up to the normal operating range.
• The air compressor should cut off again: between 120 and 140 PSI.

Optional Tug Test (After completing the above steps) 

• With the air pressure built up and the parking brake set, place the transmission in a low gear. 
• Gently pull against the parking brake. The vehicle should not move, confirming the parking brakes are holding. 

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.

How many questions are on the air brake test?

The air brake written test has a number of questions that varies by state, ranging from 20 to 30 or more multiple-choice questions, with specific tests like California’s having 25 questions and Florida having 20 questions, while other practice tests and resources might show up to 60 questions for the same endorsement. You can find the exact number of questions for your state by checking the official CDL manual or your local DMV. 
Key Information

• State-Specific: The air brake endorsement test is administered by each state, and the number of questions on the written portion can vary. 
• Common Question Count: Many states have a written test with 20 to 25 questions, but some can have more. 
• Official Source: The most accurate source for the number of questions on the test in your area is your state’s official CDL manual. 
• Passing Score: Regardless of the number of questions, you will typically need to score 80% or higher to pass the written exam. 

What is the correct order of steps for a pre-trip air brake inspection?

If it’s an older. System you’re going to drain the wet tank uh and we talked about how to find the wet tank. And you’re going to do that to check the one-way check valves.