ELDT Pre- and Post-Trip Inspections 3 — Questions and Answers
Question 1: When checking the brakes during a pre-trip, what indicates a problem with the slack adjusters on S-cam brakes?
- They move less than 1 inch when pulled
- The pushrod travels more than about 1 inch when pulled by hand (Correct answer)
- They are cool to the touch
- They are painted yellow
Correct answer: The pushrod travels more than about 1 inch when pulled by hand
If the slack adjuster moves more than about one inch, the brakes likely need adjustment.
Question 2: During the air brake check, at what point should the low air pressure warning activate?
- At 90 PSI
- Below 60 PSI (typically around 55 PSI) (Correct answer)
- At exactly 120 PSI
- Only when the engine stalls
Correct answer: Below 60 PSI (typically around 55 PSI)
The low air pressure warning must come on before pressure drops below 60 PSI.
Question 3: What does a static air leak test check for?
- Engine oil pressure
- Air pressure loss with the engine off and brakes released/applied (Correct answer)
- Coolant temperature
- Tire tread depth
Correct answer: Air pressure loss with the engine off and brakes released/applied
With the engine off you check that air loss stays within allowed limits for the parking brake condition.
Question 4: At approximately what pressure should the spring/parking brakes automatically apply during the air loss test?
- Between 20 and 45 PSI (Correct answer)
- At 90 PSI
- At 110 PSI
- They never apply automatically
Correct answer: Between 20 and 45 PSI
The spring brakes should pop out (apply) somewhere between 20 and 45 PSI.
Question 5: How do you test that the service brakes are working during a pre-trip?
- Rev the engine loudly
- Move forward slowly and firmly apply the brake pedal, checking for pull or delay (Correct answer)
- Honk the horn
- Check the tire pressure
Correct answer: Move forward slowly and firmly apply the brake pedal, checking for pull or delay
Roll forward at low speed and apply the brakes to confirm they stop the vehicle without pulling to one side.
Question 6: What should you inspect on the brake drums or discs during the walk-around?
- That they are wet with oil
- For cracks, and that linings are not worn dangerously thin (Correct answer)
- That they are warm
- Only their color
Correct answer: For cracks, and that linings are not worn dangerously thin
Check drums/discs for cracks and ensure brake linings/pads are not worn too thin or contaminated by oil.
Question 7: What does the build-up rate test on an air brake system verify?
- That pressure builds from 85 to 100 PSI within a set time at operating RPM (Correct answer)
- That the horn is loud
- That the tires are inflated
- That the mirrors are clean
Correct answer: That pressure builds from 85 to 100 PSI within a set time at operating RPM
The compressor should build air pressure from 85 to 100 PSI within about 45 seconds at operating RPM.
ELDT Pre- and Post-Trip Inspections 3
When checking the brakes during a pre-trip, what indicates a problem with the slack adjusters on S-cam brakes?