Air Brake System Quiz

An air leak at point 'X' in the system shown above would cause which of these to leak down?

• tank only

• tank only

• 2 and 4 tanks only

• the entire system

The slack adjuster shown above is being adjusted. Technician A says that travel 'X' should be as short as possible without dragging the brakes. Technician B says that angle 'Y' should be less than 90 degrees when the brakes are applied. Who is right?

• Technician A only

• Technician B only

• Both A and B

• Neither A or B

Which of the following cannot cause a drum on an air-braked vehicle to overheat?

• an over-tightened brake adjuster at that wheel

• under-adjusted brake(s) elsewhere on the vehicle

• too-high governor cut-out pressure

• driving downhill in too high a gear

All the brakes drag on a school bus with hydraulic brakes. Which of the following could be the cause?

• air in the hydraulic system

• too high a vacuum supply to the power brake booster

• a leaking secondary cup in the master cylinder

• no brake pedal free travel

Which of the following could cause a pulsating brake pedal on a school bus with hydraulic brakes?

• zero brake pedal free travel

• glazed linings

• an out-of-round brake drum

• a frozen wheel cylinder piston

In the 'AL' factor, the 'L' refers to the:

• lining’s friction code

• thickness of the lining

• type of front-brake limiting valve

• length of the slack adjuster

Technician A says that linings worn too thin on an air-braked school bus can cause the S-cam shaft to roll over. Technician B says this condition can cause excess brake pedal travel. Who is right?

• Technician A only

• Technician B only

• Both A and B

• Neither A or B

Spring brakes on an air-braked school bus must be able to hold the vehicle, facing uphill or downhill, on what percent grade?

• 10%

• 20%

• 30%

• 40%

The driver of a school bus with hydraulic brakes says the pedal reserve is too low. Technician A says the brakes could be out of adjustment. Technician B says one brake system may have failed. Who is right?

• Technician A only

• Technician B only

• Both A and B

• Neither A or B

The parking brakes fail to apply on a school bus with air brakes. Technician A says this could be caused by low air pressure in the spring brake chamber. Technician B says this could be caused by a ruptured spring brake diaphragm. Who is right?

• Technician A only

• Technician B only

• Both A and B

• Neither A or B