Air Brake Maintenance & Troubleshooting Flashcards

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

Answer: At every pre-trip inspection before operating the vehicle

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

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

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

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

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

Answer: A defective slack adjuster that should be replaced by a mechanic

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

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

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

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.

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

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

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

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

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

A cracked brake drum is a federal out-of-service condition — the vehicle must be removed from service until the drum is replaced.