How do you perform an air brake test?

How to test the air loss rate?

1. Make sure the vehicle is on the level surface and the air pressure is within the normal operating range(cut-out and cut-in).
2. Apply the wheel chocks.
3. Turn the engine off.
4. Release the spring brakes.
5. Apply and hold the service brakes for a minute.
6. Open the window and listen for the air leaks.

What is the 7 step air brake test?

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 pressure do air brakes run at?

100 to 120 psi
Normal air brake system pressure range is around 690 to 828 kPa (100 to 120 psi). Drivers should know the normal pressure range of the vehicle they operate and should report any abnormal condition.

When checking air brake system pressure the governor cut-in pressure should be?

Actual cut-in pressure must never be less than 552 kPa (80 psi ). The air brake system is defective when cut-out pressure is above 1000 kPa (145 psi ) or cut-in pressure is below 552 kPa (80 psi ).

What is the proper way to test the air leakage rate?

Test air leakage rate: With a fully-charged air system (typically 125 psi), turn off the engine, release the service brake, and time the air pressure drop. The loss rate should be less than 2 psi in 1 minute for single vehicles and less than 3 psi in 1 minute for combination vehicles.

How do air brakes on a bus work?

Air brakes work using compressed air instead of hydraulic fluid. The air compressor then pumps the air into the air storage tanks, which store the compressed air until it’s needed. Air pressure is used to apply the service brakes and release the parking brake. There are multiple air circuits in the system.

What can happen if the air pressure gets too low in an air brake system?

Pushing the pedal down harder applies more air pressure. Letting up on the brake pedal reduces the air pressure and releases the brakes. Pressing and releasing the pedal unnecessarily can let air out faster than the compressor can replace it. If the pressure gets too low, the brakes won’t work.

How should you check your air compressor governor cut in and cut out pressures?

The air governor should cut-out the air compressor at about the manufacturer’s specified pressure. The air pressure shown by your gauge(s) will stop rising. With the engine idling, step on and off the brake to reduce the air tank pressure.

What is the air brake test?

The Air Brake Test covers the different braking systems and tests you on your knowledge of parking brakes, service brakes, emergency brakes, reading low pressure warnings, checking pressure gauges, and more.

How do you test the brakes on a school bus?

TEST 1: Parking brake test. 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. TEST 2: Applied pressure test. (With parking brake released.) Turn the bus off.

What is the normal air pressure for a bus brake?

BRAKE TEST PROCEDURES AIR OPERATED BRAKES This system is operated by air from a compressor off the engine. Normal air pressure is between 80 and 120 psi. When the system falls below approximately 60 psi, the brakes are automatically locked by springs and the bus becomes immobile. TEST 1:Parking brake test.

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.

How do I perform a spring brake test?

For the Spring Brake test, release the spring brake and have the bus roll forward very slowly. Then apply the spring brake to make sure it will stop the bus and hold itself in place