DOT Inspector Vehicle Inspection Procedures 2 — Questions and Answers
Question 1: During a DOT Level I inspection, what is the minimum brake lining thickness allowed before a brake is considered out-of-service on a steering axle?
- 1/4 inch
- 1/8 inch (Correct answer)
- 4mm
- 2mm
Correct answer: 1/8 inch
Steering axle brake lining must be at least 4mm (5/32 inch); however, the out-of-service criterion specifies no lining thickness less than 1/4 inch is permitted on steering axles.
Question 2: When inspecting air brake systems, what is the maximum allowable single-vehicle air loss rate at 90 PSI with the engine off and brakes released?
- 2 PSI per minute
- 3 PSI per minute (Correct answer)
- 4 PSI per minute
- 5 PSI per minute
Correct answer: 3 PSI per minute
FMCSA regulations allow no more than 3 PSI per minute air loss for single vehicles with brakes released.
Question 3: An inspector finds a cracked wheel in the disc area between the hand holes. What is the correct action?
- Flag for repair within 30 days
- Issue a warning and allow continued operation
- Place the vehicle out of service immediately (Correct answer)
- Allow operation if crack is less than 2 inches
Correct answer: Place the vehicle out of service immediately
Any crack in the disc area or bolt circle of a wheel is an out-of-service condition requiring immediate removal from service.
Question 4: Which of the following conditions would NOT place a vehicle out of service for steering defects?
- Loose steering wheel with more than 10 degrees of free play on a vehicle with power steering
- A steering gear box that is securely mounted but shows minor surface rust (Correct answer)
- Any part of the steering system that is broken
- Tie rod ends that are worn to the point of allowing separation
Correct answer: A steering gear box that is securely mounted but shows minor surface rust
Surface rust on a securely mounted steering gear box is not an out-of-service condition, unlike broken parts, excessive play, or worn tie rod ends.
Question 5: Under FMCSA regulations, what is the maximum allowable slack adjuster travel for a Type 30 air brake chamber with a 6.5-inch stroke?
- 1.75 inches
- 2.0 inches (Correct answer)
- 2.5 inches
- 3.0 inches
Correct answer: 2.0 inches
A Type 30 brake chamber with a 6.5-inch stroke has a maximum allowable pushrod travel of 2.0 inches before being considered out of service.
Question 6: When checking fifth wheel coupling during an inspection, which of the following indicates a defective condition?
- Minor surface rust on the plate
- Visible movement between the upper and lower halves under applied tug test (Correct answer)
- Grease present on the fifth wheel plate
- A locking jaw that clicks audibly when engaged
Correct answer: Visible movement between the upper and lower halves under applied tug test
Visible movement between fifth wheel halves during a tug test indicates locking jaw failure and is an out-of-service condition.
Question 7: During a vehicle inspection, an inspector discovers the front axle left spring hanger is cracked at the mounting point. What action should be taken?
- Note defect and schedule repair within 7 days
- Allow operation at reduced speed
- Place the vehicle out of service (Correct answer)
- Issue a repair order with 30-day compliance
Correct answer: Place the vehicle out of service
A cracked or broken spring hanger is a critical suspension defect that requires immediate out-of-service placement under FMCSA 393.207.
DOT Inspector Vehicle Inspection Procedures 2
During a DOT Level I inspection, what is the minimum brake lining thickness allowed before a brake is considered out-of-service on a steering axle?