Podcast
Questions and Answers
All vehicles with air brakes are required to have a low pressure warning signal. What could it be?
All vehicles with air brakes are required to have a low pressure warning signal. What could it be?
- A red light
- A wig wag mechanical arm
- A buzzer
- Any of the above (correct)
To test the low pressure warning signal, you should do all BUT the following...
To test the low pressure warning signal, you should do all BUT the following...
- Step on and off the brake pedal to reduce air pressure
- Shut the engine off
- Ask a friend to listen for the signal (correct)
- Turn the electrical power on
If your truck or bus has dual parking control valves, it means that you can use pressure from a separate tank to:
If your truck or bus has dual parking control valves, it means that you can use pressure from a separate tank to:
- Release the spring brakes to move a short distance (correct)
- Stay parked without using up service air pressure
- Balance the service brake system
- Apply more brake pressure if the main tank is getting low
When the low pressure warning is activated, you should...
When the low pressure warning is activated, you should...
Your truck or bus has a dual air brake system. If a low air pressure warning comes on for only one system, what should you do?
Your truck or bus has a dual air brake system. If a low air pressure warning comes on for only one system, what should you do?
To test your service brakes you should...
To test your service brakes you should...
Stab braking occurs when you...
Stab braking occurs when you...
You should know that your brakes are fading when:
You should know that your brakes are fading when:
Air brake equipped vehicles must have:
Air brake equipped vehicles must have:
The brake pedal in an air brake system:
The brake pedal in an air brake system:
The proper way to go down long grades is to...
The proper way to go down long grades is to...
The governor stops pumping air when it reaches the 'cut out' level, or around...
The governor stops pumping air when it reaches the 'cut out' level, or around...
Compressed air is stored...
Compressed air is stored...
A straight truck or bus air brake system should not leak at a rate of more than ____ PSI per minute with the engine off and the brakes released.
A straight truck or bus air brake system should not leak at a rate of more than ____ PSI per minute with the engine off and the brakes released.
The air compressor governor controls:
The air compressor governor controls:
The governor allows the air to start pumping again when it reaches the cut in level, or around...
The governor allows the air to start pumping again when it reaches the cut in level, or around...
During normal driving, spring brakes are usually held back by:
During normal driving, spring brakes are usually held back by:
To make an emergency stop with air brakes, using the stab braking method, you should:
To make an emergency stop with air brakes, using the stab braking method, you should:
In a single vehicle with a fully charged air system, air pressure loss (after an initial drop) should be less than...
In a single vehicle with a fully charged air system, air pressure loss (after an initial drop) should be less than...
The brake system that applies and releases the brakes when the driver uses the brake pedal is the:
The brake system that applies and releases the brakes when the driver uses the brake pedal is the:
To determine if slack adjusters need adjustment...
To determine if slack adjusters need adjustment...
You should avoid using the parking brake...
You should avoid using the parking brake...
A combination vehicle air brake system should not lose air faster than...
A combination vehicle air brake system should not lose air faster than...
Some air brake systems have an alcohol evaporator which helps...
Some air brake systems have an alcohol evaporator which helps...
Air tanks should be drained...
Air tanks should be drained...
To check the air compressor governor 'cut in' and 'cut out' pressures...
To check the air compressor governor 'cut in' and 'cut out' pressures...
Air tanks should be drained...
Air tanks should be drained...
The service brake system...
The service brake system...
Air brakes take longer to stop than hydraulic brakes because...
Air brakes take longer to stop than hydraulic brakes because...
The driver must be able to see a warning that is given before air pressure in the service air tanks falls below:
The driver must be able to see a warning that is given before air pressure in the service air tanks falls below:
If the air compressor should develop a leak, what keeps the air in the tanks?
If the air compressor should develop a leak, what keeps the air in the tanks?
If your air compressor stops working...
If your air compressor stops working...
The safety valve in the air compressor tank is set to open at...
The safety valve in the air compressor tank is set to open at...
An air tank is equipped with a drain valve to remove...
An air tank is equipped with a drain valve to remove...
The application pressure gauge shows the driver how much pressure:
The application pressure gauge shows the driver how much pressure:
Brake drums...
Brake drums...
To test the air leakage rate you should...
To test the air leakage rate you should...
A dual air brake system...
A dual air brake system...
Oil and water usually collected in compressed air tanks. If you do not have an automatic tank drain, when should you drain the air tanks?
Oil and water usually collected in compressed air tanks. If you do not have an automatic tank drain, when should you drain the air tanks?
Slack adjusters...
Slack adjusters...
Study Notes
Air Brakes System Overview
- Air brake systems in vehicles must include a low-pressure warning signal, which can be a red light, a mechanical arm, or a buzzer.
- Testing the low-pressure warning signal involves shutting off the engine, turning on electrical power, and stepping on the brake pedal.
Dual Parking Control Valves
- Dual parking control valves allow releasing spring brakes using pressure from a separate tank to move a short distance.
Low Pressure Warning Protocol
- If the low-pressure warning is activated, bring the vehicle to a safe stop while controlling the brakes.
- A dual air brake system warning for one system requires safe parking until fixed.
Brake Testing and Techniques
- To test service brakes, move forward slowly while releasing the parking brake and pressing the brake pedal.
- Stab braking involves hard braking followed by releasing the brakes to prevent wheel lock.
Brake Performance Indicators
- Brake fading is indicated by increased effort needed to control speed on a downgrade.
- Automatic slack adjusters can be checked by releasing both service and parking brakes.
Air Brake Equipment Requirements
- Air brake systems must have a supply pressure gauge.
- They should not leak at rates exceeding 2 psi per minute when parked and released.
Compressor and Air Tank Operation
- The air compressor governor controls the pumping of air into tanks, with cut-out levels around 125 psi and cut-in levels around 100 psi.
- Air pressure should be maintained between cuts to ensure brake effectiveness.
Safety and Maintenance Guidelines
- Draining air tanks should be performed daily to avoid sludge buildup that can clog valves.
- Oil and water in tanks need to be removed regularly, ideally daily if there’s no automatic drain.
Brake System Components
- The service brake system applies and releases brakes under normal driving conditions.
- Brake drums house the brake shoes and linings, and they are bolted to the vehicle’s wheels.
Emergency Procedures
- In case of compressor failure, air pressure in tanks will remain temporarily, but brakes may lose effectiveness over time.
- A safety valve prevents over-pressurization, typically set to open at 150 psi.
Additional Brake Characteristics
- Air brakes react slower than hydraulic ones due to the time needed for air to travel through the system.
- The application pressure gauge informs the driver about the pressure applied to the brakes.
Adjustment and Leak Testing
- Slack adjusters can be adjusted manually or automatically but should be checked regularly.
- Testing air leakage rates is important, and should be done with the engine off for accuracy.
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Description
Prepare for your CDL Class A air brakes test with these flashcards. Each card focuses on essential knowledge regarding air brake systems, including low pressure warning signals and testing procedures. Study effectively and ensure you're ready for the exam!
