CDL Class A Air Brakes Test Flashcards
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Questions and Answers

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...

  • 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:

  • 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...

    <p>Bring the vehicle to a safe stop while you still control the brakes</p> Signup and view all the answers

    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?

    <p>Stop, safely park, and continue only after the system is fixed</p> Signup and view all the answers

    To test your service brakes you should...

    <p>Release the parking brake, move forward slowly, and depress brakes</p> Signup and view all the answers

    Stab braking occurs when you...

    <p>All of the above</p> Signup and view all the answers

    You should know that your brakes are fading when:

    <p>You have to push harder on the brake pedal to control your speed on a downgrade</p> Signup and view all the answers

    Air brake equipped vehicles must have:

    <p>A supply pressure gauge</p> Signup and view all the answers

    The brake pedal in an air brake system:

    <p>Controls the air pressure applied to put on the brakes</p> Signup and view all the answers

    The proper way to go down long grades is to...

    <p>Use a low gear and apply light pressure on the brakes</p> Signup and view all the answers

    The governor stops pumping air when it reaches the 'cut out' level, or around...

    <p>125 psi</p> Signup and view all the answers

    Compressed air is stored...

    <p>In the storage tank</p> Signup and view all the answers

    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.

    <p>2</p> Signup and view all the answers

    The air compressor governor controls:

    <p>When air is pumped into the air tanks</p> Signup and view all the answers

    The governor allows the air to start pumping again when it reaches the cut in level, or around...

    <p>100 psi</p> Signup and view all the answers

    During normal driving, spring brakes are usually held back by:

    <p>Air pressure</p> Signup and view all the answers

    To make an emergency stop with air brakes, using the stab braking method, you should:

    <p>Brake as hard as you can, get off the brakes when the wheels lock, get back on the brakes when the wheels start rolling again</p> Signup and view all the answers

    In a single vehicle with a fully charged air system, air pressure loss (after an initial drop) should be less than...

    <p>2 psi per minute</p> Signup and view all the answers

    The brake system that applies and releases the brakes when the driver uses the brake pedal is the:

    <p>Service brake system</p> Signup and view all the answers

    To determine if slack adjusters need adjustment...

    <p>Release both the service and parking brakes</p> Signup and view all the answers

    You should avoid using the parking brake...

    <p>When the brakes are hot</p> Signup and view all the answers

    A combination vehicle air brake system should not lose air faster than...

    <p>3 psi per minute</p> Signup and view all the answers

    Some air brake systems have an alcohol evaporator which helps...

    <p>Reduce the risk of ice in the air brake valves during cold weather</p> Signup and view all the answers

    Air tanks should be drained...

    <p>Once a day</p> Signup and view all the answers

    To check the air compressor governor 'cut in' and 'cut out' pressures...

    <p>All of the above</p> Signup and view all the answers

    Air tanks should be drained...

    <p>All of the above</p> Signup and view all the answers

    The service brake system...

    <p>Applies and releases the brakes by using the brake pedal under normal driving</p> Signup and view all the answers

    Air brakes take longer to stop than hydraulic brakes because...

    <p>It takes longer for the air to flow through the lines</p> Signup and view all the answers

    The driver must be able to see a warning that is given before air pressure in the service air tanks falls below:

    <p>60 psi</p> Signup and view all the answers

    If the air compressor should develop a leak, what keeps the air in the tanks?

    <p>The one way check valve</p> Signup and view all the answers

    If your air compressor stops working...

    <p>You'll still have air pressure left in the air tanks</p> Signup and view all the answers

    The safety valve in the air compressor tank is set to open at...

    <p>150 psi</p> Signup and view all the answers

    An air tank is equipped with a drain valve to remove...

    <p>Water and oil</p> Signup and view all the answers

    The application pressure gauge shows the driver how much pressure:

    <p>Is being applied to the brakes</p> Signup and view all the answers

    Brake drums...

    <p>All of the above</p> Signup and view all the answers

    To test the air leakage rate you should...

    <p>Turn off the engine and release the service brake</p> Signup and view all the answers

    A dual air brake system...

    <p>Has two air brake systems and one set of controls</p> Signup and view all the answers

    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?

    <p>After every working day</p> Signup and view all the answers

    Slack adjusters...

    <p>Can be adjusted manually or automatically</p> Signup and view all the answers

    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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    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!

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