CDT Vehicle Operations & Maintenance 3

Question 1

What does the 'pushrod travel' measurement indicate during an air brake inspection?

Accepted Answer

The distance a brake chamber pushrod moves when brakes are applied

Answer

Pushrod travel (stroke) measures how far the pushrod extends when brakes are applied; excessive travel indicates out-of-adjustment brakes.

Question 2

When coupling a semi-trailer to a tractor, the LAST step before moving should be:

Accepted Answer

Tug test — pull forward against locked trailer brakes to confirm coupling

Answer

The tug test confirms the kingpin is properly locked in the fifth wheel jaws before the driver moves the combination vehicle.

Question 3

What is the purpose of automatic slack adjusters on commercial vehicles?

Accepted Answer

To maintain proper brake adjustment as linings wear

Answer

Automatic slack adjusters continuously maintain the correct distance between the brake lining and drum as linings wear, reducing manual adjustment needs.

Question 4

A driver smells something burning after a long downhill grade. The MOST likely cause is:

Accepted Answer

Overheated service brakes from excessive use

Answer

A burning smell after a downgrade almost always indicates overheated brake drums and linings from excessive brake use instead of proper engine braking.

Question 5

Under FMCSA regulations, which defect found during a pre-trip inspection requires the vehicle to be placed Out of Service immediately?

Accepted Answer

A cracked brake drum

Answer

A cracked brake drum is an Out of Service condition per FMCSA regulations because it compromises braking effectiveness and safety.

(CDT) Certified Driver Trainer Practice Test

(CDT) Certified Driver Trainer Practice Test

CDT Vehicle Operations & Maintenance 3