Use this checklist as a guide when completing an inspection of air brake system operation.
Note: When performing this inspection as part of a practical examination, indicate to the examiner what you are testing at the beginning of each segment.
Prepare the vehicle for inspection:
- Apply the spring brakes.
- Put wheel chocks or blocks in place.
- Ensure air pressure is at least 621 kPa (90 psi). (If air pressure is too low, warning will activate as soon as ignition key is turned on.)
- Ensure key is ‘on’. Engine may be running or shut off. (If ignition key is not turned on the warning will not activate.)
- Press and release the brake pedal several times until the low air warning device activates.
- Watch the pressure gauges and note the pressure value when the low air warning device activates. (Warning may be only a light or a light and an audible device.)
If the device fails to activate or activates below 380 kPa (55 psi), the vehicle is defective.
Test air pressure build-up time
- If the vehicle has a trailer attached, ensure the trailer supply valve is closed (pulled out).
- Reduce air pressure to below 552 kPa (80 psi).
- Maintain engine speed of 600 to 900 rpm.
- Observe time for pressure to rise from 587 to 690 kPa (85 to 100 psi) while maintaining specified engine speed.
If the air pressure build-up time is greater than two minutes, the vehicle is defective.
Report defective vehicle conditions
Drivers are required to report defective vehicle conditions.
It is illegal to operate or drive a defective vehicle.Test air compressor governor settings
- Observe the air pressure gauges until pressure ceases climbing. (Air dryer purge also signals compressor cut-out.)
- Reduce air pressure slowly and note the point where pressure begins to climb again. (A change in the sound of the air compressor also signals compressor cut-in.)
If cut-out pressure is greater than 932 kPa (135 psi) or is less than 690 kPa (100 psi) and/or cut-in pressure is less than 552 kPa (80 psi) the vehicle is defective.
Test air loss rate
- Ensure vehicle is secure and release the spring brakes.
- Ensure air system pressure is between cut-in and cut-out settings and shut off the engine.
- Press and hold the brake pedal in the fully applied position.
- Observe the air pressure gauges for one minute and note any change in air pressure. (Disregard the initial pressure drop and begin test after pressure has stabilized.)
If the pressure drop exceeds the value specified for the vehicle, the vehicle is defective.
Test tractor (towing vehicle) protection valve
- Ensure air pressure is within its normal operating range.
- Ensure the trailer supply valve is closed (pulled out).
- Remove the trailer service line coupler from the trailer or its storage location and place it where it can be observed.
- Press and hold the brake pedal. (Note: If concerned that the vehicle has no anti-compounding valve, ensure the vehicle is secure and release the spring brakes before applying service brakes.)
- Note whether air exhausts from the trailer service line coupler.
If air exhausts from the trailer service line, the vehicle is defective.
Test automatic application of the trailer spring brakes
- Ensure trailer supply valve is open (pushed in), air pressure is in the normal operating range and trailer is fully charged.
- Close (pull out) the trailer supply valve. (Note: The trailer supply line may also be disconnected but this practice is not recommended while the line is under pressure.)
- Air should be heard exhausting from the trailer spring brakes. (Note: If uncertain that the trailer spring brakes have applied, gently apply engine power to confirm brake application.)
If the trailer spring brakes do not apply, the vehicle is defective.
Test spring (parking/emergency) brakes
- Apply the spring brakes.
- Remove wheel chocks or blocks.
- Apply engine power gently to the wheels and observe the vehicle response.
If the spring brakes fail to hold the vehicle stationary, the vehicle is defective.
Inspect air tank drain valves
- Ensure air system pressure is within its normal operating range.
- Drain the supply tank until it discharges only clean air.
- Drain the remaining air tanks.
- Watch the discharge from the air tanks and ensure that the drain valves function properly.
If any drain valve fails to function properly, the vehicle is defective.
Report defective vehicle conditions.
Drivers are required to report defective vehicle conditions. It is illegal to operate or drive a defective vehicle.