How do you do a air brake test?
- Make sure the air pressure is above 100psi – 120psi.
- Turn the key to the off position.
- Turn the key to the on position, do not start the truck.
- Press both air brake valves in, red valve first then yellow in second.
- Air pressure will drop, allow pressure to stabilize.
How do I test my air brakes?
Test service brake by accelerating to 5mph and pressing brake pedal. If vehicle pulls to one side, this indicates a brake alignment problem. If there is a problem discovered while testing the Air Brakes, do not drive the vehicle. It is your responsibility to make sure it is repaired by a mechanic. Never operate a vehicle that is unsafe to drive.
How do air brakes work on a school bus?
Air Brakes are standard equipment on many school buses. Generally, air brakes are used on heavy duty vehicles. Air brakes work by the compression of air. Compressed air activates the brakes and causes the bustoo stop.
Where are the brakes located on a bus?
On a bus: •Primary brakes are located on the center and rear axles. •Secondary brakes are located on front or the steer axle. Brake Balance
How to pass the first time with air brakes?
IMPORTANT – AIR BRAKES HOW to PASS the First Time!!! The Seven-Step Air Brake check is designed to test the governor cut-in and cut-out pressures, air pressure leakage, warning buzzer, brake valves and air pressure rebuild rates. Brakes off means the yellow and/or red valve is pushed in (on = valve out).
What are the ABCs of air brakes?
What are the three basic circuits of an air brake system?
What is the diaphragm on a brake?
What is the heart of an air brake system?
How many inches does a brake pedal stroke?
What is a wedge brake?
When the foot valve is at rest, what happens to the brakes?
See more
What is the standard procedure for checking your air brake system?
Stop the vehicle, put the parking brake on, and gently pull against it in a low gear to test that the parking brake will hold. Test Service Brakes. Wait for normal air pressure, release the parking brake, move the vehicle forward slowly (about five mph), and apply the brakes firmly using the brake pedal.
How do you use air brakes on a school bus?
7:039:31Lessons in School Bus Air brakes - YouTubeYouTubeStart of suggested clipEnd of suggested clipOnly when the service brake pedal is depressed. Each time the operator releases the service brakeMoreOnly when the service brake pedal is depressed. Each time the operator releases the service brake here that was used to slow the vehicle is released from the system.
What is the first step of the air brake test?
To perform this test, the driver must start with the engine running and with the air pressure built to governor cut-out (120–140 psi or another level specified by the manufacturer).
How many steps are used in checking the air brake system?
The 9-Step CDL Air Brake Test. Static Air Leakage. Turn off the engine with a fully-charged air system. Then, release the parking brake and time the air pressure drop.
How do you check brakes on a bus?
Start the bus and let the air pressure build to at least 90 psi. Step on the brake pedal and put the bus into gear. Slowly take your foot off the brake and gently press the accelerator. The bus should not move.
How do you do a brake test?
17:2823:10How to Do the CDL Air Brake Pre-Trip Inspection - YouTubeYouTubeStart of suggested clipEnd of suggested clipIn the last part of the pre-trip inspection is going to be a tug test on the parking brakes and aMoreIn the last part of the pre-trip inspection is going to be a tug test on the parking brakes and a response test on the service brake so what you're going to do is apply the parking brakes get out
What is the cut in pressure on a school bus?
Pressure should be approximately 40 PSI. 12. Restart engine and rebuild pressure to 120-140 PSI or governor cut-out.
What can happen if the air pressure gets too low in an air brake system?
The brakes will be very sensitive. Explanation Pressing and releasing the brake pedal unnecessarily can let air out faster than the compressor can replace it, reducing the available air pressure. If the air pressure in an air brake system gets too low, the brakes will no longer work.
Which of the following are you testing when you do the air brake test?
Inspecting Air Brakes While in the vehicle, you will need to test the air leakage rate, the low-pressure warning alarm, and that the spring brakes come on automatically. You need to test the air pressure build-up rate and the governor cut-in/cut-out pressures as well as performing the service and parking brake tests.
How can you manually check the slack adjusters?
With service brakes in the released position, mark the push rod even with the brake chamber. Make a full brake application and mark the push rod again. Measure between the two marks to determine the length of push-rod travel (stroke).
How do you check an air brake governor?
2:457:20How to Test The Governor for Air Brakes Course - YouTubeYouTubeStart of suggested clipEnd of suggested clipThrottle up a little bit and watch the needles climb if the needles are climbing you know that theMoreThrottle up a little bit and watch the needles climb if the needles are climbing you know that the governor has put the compressor back into the load phase.
How long should it take for air brakes to build pressure?
45 secondsAir pressure build-up from 85 psi to 100 psi should take 45 seconds or less. While driving, observe the air pressure gauge during build-up to ensure proper air system operation.
Bus Air Brake System Training
Related APTA Standards •APTA BTS-BC-RP-005-10, Rev. 1: Troubleshooting Common Transit Bus S-cam and Air Brake Complaints •APTA BTS-BC-RP-006-17: Transit Bus Air Disc Brake Operation and Wheels On Inspection •APTA BTS-BC-RP-007-17: Transit Buss Air Disc Brake Wheel Off Inspection and
Dual Air Brake System - School Bus Driver Class
Air Brake Manual • 55 In the illustration, air is pumped by the compressor (1) to the supply/wet reservoir (5) (blue), which is protected from over pressurization by a safety
How do you drive with air brakes?
To apply the air brakes during normal stops, push the brake pedal down. Control the pressure so the vehicle comes to a smooth, safe stop. If you have a manual transmission, do not push the clutch in until the engine RPM is down close to idle. When stopped, select a starting gear.
Is it hard to drive with air brakes?
Are you training to drive for Baltimore County? It’s very difficult to get air brakes to stop as smoothly as hydraulic. Air can be compressed, brake fluid can’t. When you apply pressure at one end of a hydraulic brake line, the same amount of pressure is immediately transferred to the other end.
Do school buses have air brakes?
Every school bus with a includes compressed air compressed air service brake portion of air over system shall have: hydraulic systems.
Is driving with air brakes different?
But there is a big difference between operating vehicles with hydraulic braking systems and air braking systems. Air, or more correctly, air pressure is what allows your truck air brakes to operate properly. If the pressure is weak the brakes won’t engage properly.
What happens if you pull the air brake while driving?
You suddenly pull the parking brake and the entire force hit the wheels of your vehicle. The rear and front tires suppose to absorb the entire force, but instead, the rear wheel locks up and skid. The chances are that the entire car starts to slide sideways, which is more dangerous than you can even imagine.
Why must air tanks be drained?
Why must air tanks be drained? Water and compressor oil can get inside of the tank and can freeze in cold weather and cause brake failure. When the air pressure is removed the springs put on the brakes. A parking brake control in the cab allows the driver to let the air out of the brakes.
Can I drive air brakes without CDL?
There has been some confusion as to whether a CDL is required when driving a truck with air brakes. For example, a person can drive a straight truck with a gross vehicle weight rating of 26,000 (under 26,001 lbs.) with air brakes, and no CDL is required.
How do you use air brakes on a bus?
To apply the air brakes during normal stops, push the brake pedal down. Control the pressure so the vehicle comes to a smooth, safe stop. If you have a manual transmission, do not push the clutch in until the engine RPM is down close to idle. When stopped, select a starting gear.
How do you drive a school bus with air brakes?
When braking with air brake systems, the driver should push the brake pedal down and hold it in place until the vehicle comes to a smooth stop.
Why do buses use air brakes?
Air brakes are used in heavy commercial vehicles due to their reliability. They have several advantages for large multi-trailer vehicles: The supply of air is unlimited, so the brake system can never run out of its operating fluid, as hydraulic brakes can. Minor leaks do not result in brake failures.
How do you check air brakes on a bus?
Start the bus and let the air pressure build to at least 90 psi. Step on the brake pedal and put the bus into gear. Slowly take your foot off the brake and gently press the accelerator. The bus should not move.
Why must air tanks be drained?
Why must air tanks be drained? Water and compressor oil can get inside of the tank and can freeze in cold weather and cause brake failure. When the air pressure is removed the springs put on the brakes. A parking brake control in the cab allows the driver to let the air out of the brakes.
What happens if you pull the air brake while driving?
You suddenly pull the parking brake and the entire force hit the wheels of your vehicle. The rear and front tires suppose to absorb the entire force, but instead, the rear wheel locks up and skid. The chances are that the entire car starts to slide sideways, which is more dangerous than you can even imagine.
Is it hard to drive with air brakes?
Are you training to drive for Baltimore County? It’s very difficult to get air brakes to stop as smoothly as hydraulic. Air can be compressed, brake fluid can’t. When you apply pressure at one end of a hydraulic brake line, the same amount of pressure is immediately transferred to the other end.
What is the most important thing on a school bus?
There's nothing more important on any school bus than the braking system. Even if you are spending most of your driving time with a particular type of brake system on your bus, it is a good idea to familiarize yourself with both hydraulic and air brake systems.
Why does my bus pull to one side?
As previously mentioned, if you feel the bus pull to one side or the other, it is a clear indication that there is something wrong with the brakes. This could be caused by a number of factors within the break caliper system; for example rotors, and or the brake shoes on the bus may not be working properly and need maintenance. Also, if there is an unusual feel, or a delayed stopping action, when applying the brakes, it is also an indication that there is a problem with the brakes.
Do you need to test brakes on a school bus?
With that being said, every bus driver will need to accurately and meticulously ensure that the brakes on their school bus are safe.
Do air brakes require a check?
Unlike the hydraulic brake system, air brake systems require a more in depth system check .Air brake safety devices may vary. However, the following procedures are designed to make surethat all safety devices operate correctly. Keep in mind that brake tests on buses with air brakesystems are a complicated issue.
What are the ABCs of air brakes?
The ABCs of Air Brakes for School Bus Drivers. Air brakes are a wonderful, time-proven invention. Although they’ve been around for several decades, many new school bus drivers have no experience with them. This article is aimed at helping drivers understand the function and operation of air brakes.
What are the three basic circuits of an air brake system?
There are three basic circuits in all modern air brake systems: The charging system that supplies air for the brake system. The service system that is used for normal braking. The emergency/parking system which, as the name implies, is used in an emergency and for parking. The air compressor.
What is the diaphragm on a brake?
Within each brake chamber is a diaphragm. One side of the diaphragm is exposed to the air pressure from the foot valve (service air), while the other side is exposed to atmospheric pressure. As service air pressurizes the diaphragm, it pushes against a metal disc that has a metal rod attached to its center.
What is the heart of an air brake system?
The heart of the air brake system is the compressor, which is often directly coupled to the engine. It also can be engine mounted or belt driven. In all cases, the compressor turns any time the engine turns. Most compressors are fed oil directly from the engine’s pressurized oil system. The majority of compressors also use ...
How many inches does a brake pedal stroke?
Typically, the maximum stroke is 1.75 to 2.5 inches, depending on the size and type (standard vs. longstroke; front vs. rear) of the brake chamber.
What is a wedge brake?
This lever arm is called a slack adjuster and is the point where the brakes are adjusted. Wedge brakes are a variation to the above. The brake chamber pushes directly on a wedge to move the brake shoes against the brake drum, thus eliminating the need for an “S” cam. Wedge brakes are rarely used on school buses.
When the foot valve is at rest, what happens to the brakes?
When the foot valve is at rest, no service air flows to the brake chambers, and the brakes at each wheel are released (assuming the parking/emergency system is not activated). As the valve is depressed, regulated air pressure is supplied to each service brake chamber.
