OPERATION
Index-8 / Pre-Trip Inspections
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5-1.6 Brake Testing
Brake Testing
Secure all loose articles in cab, fasten seat belts, and start the engine.
Test Parking Brake
1. Allow vehicle to move forward slowly.
2. Apply parking brake.
If vehicle does not stop, bring it to a stop using the service brakes and have the problem repaired by a qualified
truck service facility.
Test Service Brake Stopping Action
1. Accelerate to about five miles per hour.
2. Push brake pedal firmly.
Excessive pulling to one side or the other, unusual brake pedal “feel,” or delayed stopping action may indicate a
problem. Have the problem diagnosed and repaired by a qualified truck service facility.
Test Dual Air Brake System Warning Light and Buzzer
NOTE: If the warning signal doesn’t work, the vehicle could lose air pressure without the knowledge of
the operator. This will reduce the effectiveness of the brakes and increase stopping distance.
Have the problem diagnosed and repaired by a qualified truck service facility.
A dual air brake system has two separate air brake systems that use a single set of brake controls. Each system
has its own air tank, hoses, lines, etc. One system typically operates the regular brakes on the rear axle or axles.
The other system operates the regular brakes on the front axle. The first system is called the “primary” system.
The other is called the “secondary” system.
1. Allow time for the air compressor to build up a minimum of 110-psi pressure in both the primary and secondary
systems.
2. Shut the engine off when the air pressure rises sufficiently to shut off the low pressure light and buzzer.
3. Shut the ignition switch off and step on and off the brake pedal to reduce air tank pressure.
4. Note the pressure at which the low air pressure warning signal alarm begins. Alarm should signal before the
pressure drops to less than 60 psi in the air tank with the lowest air pressure.
Test That the Spring Brakes Come On Automatically
The parking brakes should engage any time brake pressure drops below 40 psi. Test this function as follows:
1. Chock the wheels.
2. Allow air pressure to build sufficiently to release the parking brakes.
3. Step on and off the brake pedal to reduce the air tank pressure. The “parking brake” knob should pop out when
the air pressure falls to 40 psi. This will engage the spring brakes and help to prevent the vehicle from moving.
PRE-TRIP AND DAILY VEHICLE INSPECTIONS
PERFORM DAILY AT THE BEGINNING OF EVERY WORK PERIOD
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