310T Practical Skills and Training 2 — Questions and Answers
Question 1: When performing a brake chamber stroke check on a service brake, the pushrod stroke must not exceed which limit to pass inspection?
- The maximum stroke marked on the chamber
- 50% of the chamber's rated stroke
- The readjustment limit specified by FMCSA (Correct answer)
- 2 inches regardless of chamber size
Correct answer: The readjustment limit specified by FMCSA
FMCSA regulations define readjustment limits for each brake chamber size, and a stroke exceeding that limit requires immediate adjustment.
Question 2: A technician notices the air dryer purge valve is leaking continuously. The MOST likely cause is:
- Contaminated desiccant cartridge
- Failed purge valve solenoid or seat (Correct answer)
- Low compressor output pressure
- Cracked air dryer housing
Correct answer: Failed purge valve solenoid or seat
A continuously leaking purge valve typically indicates a failed solenoid, a worn valve seat, or debris preventing the valve from fully seating.
Question 3: When adjusting automatic slack adjusters on S-cam brakes, if adjustment continues to back off after the wheels turn, what is indicated?
- The adjuster is functioning correctly
- The slack adjuster needs replacement
- The brake shoes are worn beyond limit
- The S-cam bushings are worn (Correct answer)
Correct answer: The S-cam bushings are worn
Automatic slack adjusters that repeatedly back off often indicate worn S-cam bushings or tubes, which prevent proper cam rotation and cause the adjuster to reset.
Question 4: What is the correct procedure when bleeding air from hydraulic brake lines on a coach equipped with a hydroboost system?
- Bleed with engine off and hydraulic system depressurized
- Bleed with engine running to maintain hydraulic pressure (Correct answer)
- Use a vacuum bleeder only; pressure bleeders are prohibited
- Gravity bleed from the master cylinder only
Correct answer: Bleed with engine running to maintain hydraulic pressure
Hydroboost systems require the engine to run during bleeding so hydraulic pressure is available for proper pedal feel and complete air purging.
Question 5: During a pre-trip inspection, a driver reports the low air warning buzzer activates before the vehicle reaches operating pressure. Which component should be checked FIRST?
- Air compressor output
- Low pressure warning switch calibration (Correct answer)
- Governor cut-in and cut-out settings
- Reservoir tank drain valves
Correct answer: Low pressure warning switch calibration
If the warning activates prematurely, the low-pressure switch may be out of calibration or faulty, triggering the alarm at the wrong pressure threshold.
Question 6: A coach air conditioning system shows adequate refrigerant charge but delivers poor cooling. The technician finds the condenser coil heavily clogged. What is the DIRECT result of this condition?
- Low suction pressure and high discharge pressure
- High suction pressure and low discharge pressure
- High head pressure and reduced refrigerant subcooling (Correct answer)
- Low head pressure and excessive superheat
Correct answer: High head pressure and reduced refrigerant subcooling
A clogged condenser restricts heat rejection, causing head pressure to rise while subcooling decreases because refrigerant cannot fully condense.
Question 7: When torquing steer axle wheel nuts in a two-piece flange nut design, the correct final step is:
- Torque to spec, then back off 1/4 turn
- Torque inner nut, install outer nut, torque outer nut to spec (Correct answer)
- Torque to spec and install cotter pin without further adjustment
- Torque to spec, rotate wheel, re-torque if below minimum
Correct answer: Torque inner nut, install outer nut, torque outer nut to spec
Two-piece steer axle flange nuts require the inner nut to be torqued first, then the outer jam nut is installed and torqued to lock the assembly.
310T Practical Skills and Training 2
When performing a brake chamber stroke check on a service brake, the pushrod stroke must not exceed which limit to pass inspection?