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

Slack adjusters must be checked at every pre-trip inspection because out-of-adjustment brakes are a leading cause of brake failure.

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

Automatic slack adjusters compensate for lining wear by continuously maintaining the correct stroke length for full braking force.

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

An automatic slack adjuster that cannot maintain its own adjustment is defective and must be replaced — not repeatedly readjusted.

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

Slack adjusters should move less than 1 inch when pushed or pulled by hand with the brakes released — more movement indicates the brakes are out of adjustment.

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

FMCSA regulations require brake linings worn to 1/4 inch or less to be replaced before the vehicle is operated.

Air Brake Practice Test Practice Test

Air Brake Practice Test Practice Test

Air Brake Test Air Brake Maintenance & Troubleshooting