5 - Air Brakes

What is a dual air brake system?

• A system that uses both hydraulic and air brakes to stop the vehicle.
• A system that has two separate air brake systems, each with its own set of controls.
• A system that has two separate air brake systems, which use a single set of brake controls.
• A system that uses air brakes for the front wheels and hydraulic brakes for the rear wheels.

What are slack adjusters?

• Devices that automatically adjust the tension of the brake drums.
• Mechanical parts that connect the brake chamber push rod with the foundation brake camshaft.
• Hydraulic components that regulate brake fluid pressure.
• Electronic sensors that monitor brake pad wear.

How can you check slack adjusters?

• By measuring the air pressure in the brake lines.
• By pulling on each slack adjuster while the brakes are released; if it moves more than about one inch where the push rod attaches, it likely needs adjustment.
• By inspecting the brake pads for wear.
• By checking the brake fluid level in the master cylinder.

How can you test the low-pressure warning signal?

• By turning off the engine and observing if the warning light illuminates.
• By reducing air pressure in the system (e.g., by pumping the brake pedal) and ensuring the warning signal activates before pressure drops below 60 psi.
• By disconnecting the air compressor and checking for warning signals.
• By overinflating the air tanks and observing the warning signal.

When will the parking break knob pop out?

• (typically between 20-40 psi).
• (typically between 15-40 psi).
• (typically between 30-55 psi).
• (typically between 20-45 psi).

How can you check that the spring brakes come on automatically?

• By accelerating the vehicle and applying the parking brake
• By reducing air pressure (e.g., by pumping the brake pedal) and ensuring the parking brake knob pops out when pressure falls to the manufacturer's specification (typically between 20-45 psi).
• By manually engaging the spring brakes using a separate control.
• By inspecting the brake pads for movement.

What are the maximum leakage rates?

• Less than 1 psi per minute for single vehicles and less than 2 psi per minute for combination vehicles.
• Less than 2 psi per minute for single vehicles and less than 3 psi per minute for combination vehicles.
• Less than 3 psi per minute for single vehicles and less than 4 psi per minute for combination vehicles.
• Less than 4 psi per minute for single vehicles and less than 5 psi per minute for combination vehicles.

Why should you be in the proper gear before starting down a hill?

• To avoid engine overheating.
• To prevent the need for excessive braking, which can cause brake fade.
• To maintain optimal fuel efficiency.
• To ensure the transmission doesn't overheat.

What factors can cause brakes to fade or fail EXCEPT:

• Excessive use of the engine brake.
• Driving at high altitudes.
• Using the parking brake while driving.
• Overuse of the service brakes, causing overheating.

The use of brakes on a long, steep downgrade is only a supplement to the braking effect of the engine. True or False?

• True
• False