Air Brake Test Air Brake Maintenance & Troubleshooting

Question 1

When should slack adjusters on air brakes be checked for proper adjustment?

Accepted Answer

At every pre-trip inspection before operating the vehicle

Answer

Monthly as part of a routine maintenance schedule

Answer

Only during annual DOT inspections

Answer

Weekly during the operator's regular walk-around

Question 2

What is the purpose of an automatic slack adjuster on an air brake system?

Accepted Answer

To automatically maintain the correct clearance between brake linings and drums as linings wear

Answer

To increase air pressure delivered to the brake chambers when linings wear

Answer

To adjust air tank pressure when the compressor governor cycles off

Answer

To prevent the parking brake from releasing accidentally while parked

Question 3

An automatic slack adjuster that requires frequent manual readjustment most likely indicates what condition?

Accepted Answer

A defective slack adjuster that should be replaced by a mechanic

Answer

Normal brake wear that simply requires regular operator attention

Answer

Excessively high air pressure that is stretching the adjuster mechanism

Answer

Brake drums that are worn oversize and need to be replaced

Question 4

How do you manually check a slack adjuster for proper adjustment during a pre-trip inspection?

Accepted Answer

With brakes fully released, push and pull each slack adjuster — movement should be less than 1 inch

Answer

Apply the parking brake and attempt to rotate each slack adjuster by hand

Answer

Apply full service brake pressure and measure the temperature of each drum

Answer

Observe the angle indicator markings with full service brakes applied at 90 psi

Question 5

At what minimum brake lining thickness must drum brake linings be replaced under federal regulations?

Accepted Answer

1/4 inch (6.4 mm) at the thinnest point

Answer

1/2 inch (12.7 mm) measured at the center of the shoe

Answer

1/8 inch (3.2 mm) anywhere on the lining surface

Answer

Any thickness that passes a qualified mechanic's visual inspection

Question 6

What condition does a cracked brake drum represent under federal out-of-service criteria?

Accepted Answer

An out-of-service defect that prohibits operation until the drum is replaced

Answer

Normal aging that does not significantly affect braking performance

Answer

Minor surface cracking that can be addressed by resurfacing the drum

Answer

A condition requiring increased monitoring but not immediate repair