Commercial Drivers License (CDL) Pre-Trip Inspection: Brake Check

Pre Trip Inspection Brake Check

Parking Brake Check

  • Apply parking brake only and make sure it will hold the vehicle by shifting into a lower gear and gently pulling against the brake.

Hydraulic Brake Check

  • With the engine running, apply firm pressure to the service (foot) brake pedal and hold for five seconds.
  • The brake pedal should not move (depress) during the five seconds.
  • If equipped with a hydraulic brake reserve (backup) system, with the key off, depress the brake pedal and listen for the sound of the reserve system electric motor.
  • Check that the warning buzzer and/or light is off.
  • Check the service (foot) brake operation by moving the vehicle forward slowly (about 5 mph) and apply the brake firmly. Note any vehicle “pulling” to one side, unusual feel or delayed stopping action.

Air Brake Check (air brake equipped vehicles only)

Air brake safety devices vary. However, this procedure is designed to see that any safety device operates correctly as air pressure drops from normal to a low air condition. For safety purposes, in areas where an incline is present, you will need to use wheel chocks during the air brake check.

The proper procedures for inspecting the air brake system are as follows:

Test Air Leakage Rate (Static check)

With a fully-charged air system (typically 120 psi), turn off the engine, chock the wheels, release (push in) the parking brake button (all vehicles) and trailer air supply button (for combination vehicles) and time the air pressure drop. After the initial pressure drop, the loss rate should be no more than 2 psi in one minute for single vehicles and no more than 3 psi in one minute for combination vehicles.

Test Air Brake System for Leaks

With parking brake, (all vehicles) and trailer air supply button (for combination vehicles) released (pushed in), apply firm pressure to the service brake pedal. Watch the air supply gauge and listen for leaks. After the initial pressure drop, the loss rate for single vehicles should be no more than 3 psi in one minute and no more than 4 psi in one minute for combination vehicles. If the air loss rate exceeds these figures, have the air system repaired before operating.

Test Low Pressure Warning Alarm and/or Signal

Turn the key to the on position. Rapidly apply and release the service brake pedal to reduce air tank pressure. The low air pressure warning signal must come on before the pressure drops to less than 60 psi in the air tank. If the warning alarm/signal doesn’t work, you could be losing air pressure without knowing it. This could cause the spring brakes to activate suddenly. Only limited braking can be done before the spring brakes come on.

Check That the Spring Brakes Come on Automatically.

Continue to rapidly apply and release the service brake pedal to further reduce air tank pressure. The trailer air supply button (if it is a combination vehicle) and parking brake button should pop out when the air pressure falls to the manufacturer’s specification (usually between 20 to 40 psi). This causes the spring brakes to come on.

Check Rate of Air Pressure Buildup

When the engine is operating at 1800 RPM, the pressure should build from 85 to 100 psi within 45 seconds in dual air systems. (If the vehicle has larger than minimum air tanks, the buildup time can be longer and still be safe. Check the manufacturer’s specifications.) If air pressure does not build up fast enough, your pressure may drop too low during driving, requiring an emergency stop. Don’t drive until you get the problem fixed.

Test Service Brakes

Wait for normal air pressure, release the parking brake and trailer air supply button(for combination vehicles), move the vehicle forward slowly (about 5 mph), and apply the brakes firmly using the brake pedal. Note any vehicle “pulling” to one side, unusual feel, or delayed stopping action. This test may show you problems which you otherwise wouldn’t know about until you needed the brakes on the road.

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