AIR BRAKES

This check for air brake vehicles only.

You need not study this section unless you drive vehicles with air brakes. If you drive a vehicle equipped with a DD3 parking and emergency brake system you must tell Examiner at this point.

The Examiner will ask you to check your air supply system.

You must check the low air pressure warning system, the tractor protection valve or parking brake (spring brake), air pressure build-up and air pressure level. Examiner Says

• Make an inspection of the air supply system for your air brakes. There are four different checks to make. As you make each check, tell me what you are checking, and be specific about what you are looking for. Do you have any questions? First begin by checking the low air pressure warning system.

You Will

• Operate and check low pressure warning system by: - Turning ignition key on. - Fanning (pushes and releases brake pedal repetitively) air pressure down. - Telling the Examiner the psi when the warning buzzer/other warning device comes on (must be 60 psi or higher).

For vehicles with air brake equipped trailers:

Examiner Says

• Now, check that your trailer air supply valve (tractor protection valve) is working.

You Will

• Operate and check the trailer air supply valve by: - Pushing valve in. - Fanning down air pressure. - Tell the Examiner when the valve pops out and what the psi is (should be between 20 and 45 psi). For buses and vehicles without trailers or that have trailers not equipped with air brakes:

Examiner Says

• Now, check that your parking brake (spring brake) is working.

You Will

• Operate and check the parking brake by: - Pushing valve in. - Fanning down air pressure. - Tell the Examiner when the valve pops out and what the psi is (should be between 20 and 45 psi).

Note: Drivers who operate a vehicle equipped with the DD3 parking /emergency braking system must verbally explain how they would check and what the valve response should be when they perform a test of the spring brakes under normal pre-trip conditions.

Examiner Says

• Now check that the air pressure build-up is fast enough.

You Will

• Check air pressure build-up by: - Timing how long it takes the air pressure to increase from 50 psi to 90 psi. (The engine must be at an idle.) - Noting time. Tell the Examiner the length of build up time (must be under five minutes).

Examiner Says

• Now check the air pressure build-up to the normal operating range.

You Will

• Check air pressure build-up, and - Tell the Examiner at what psi the air compressor governor cuts off (usually between 105-125 psi). Engine may be at higher idle for this check.

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