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ASE Medium / Heavy Truck

T4 Brakes — practice test

Studying for T4 (Brakes)? Overhaul Prep has 107 verified T4 questions written to the current task list — in the same formats the real exam uses (direct, Technician A/B, EXCEPT and most-likely-cause). Every answer comes with a written explanation, so you learn why instead of memorising a letter.

107T4 questions
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9,711questions in total
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Sample T4 questions

Straight from the bank — answers highlighted, with the explanation underneath.

On an air-brake system, the primary purpose of the spring (parking/emergency) brakes is to:

  1. Provide service braking during normal driving
  2. Apply the brakes mechanically when air pressure is lost, and for parking
  3. Modulate ABS
  4. Cool the drums
WhySpring brakes are held OFF by air pressure. When pressure drops (parking valve pulled or a leak), powerful springs apply the brakes — providing fail-safe emergency and parking braking. Service braking uses the service chambers.

On a medium-duty hydraulic brake system, Technician A says DOT 3 and DOT 4 are glycol-based fluids that absorb moisture and must be kept sealed. Technician B says moisture in the fluid lowers its boiling point and can cause pedal fade under hard braking. Who is correct?

  1. Technician A only
  2. Technician B only
  3. Both Technicians A and B
  4. Neither Technician
WhyDOT 3 and DOT 4 are hygroscopic glycol-based fluids that absorb water from the air, so containers and reservoirs are kept sealed. Absorbed moisture lowers the boiling point, allowing the fluid to boil and the pedal to fade (go soft) during hard or prolonged braking.

A truck takes far longer than normal to build air pressure from 85 to 100 psi. The MOST likely cause is:

  1. A worn air compressor or a large air leak in the system
  2. Automatic slack adjusters out of adjustment
  3. A saturated air dryer desiccant cartridge
  4. A faulty ABS wheel speed sensor
WhySlow build-up points to the charging side: a compressor no longer pumping efficiently or a significant leak bleeding air as fast as it is made. Slack adjusters, desiccant, and wheel sensors do not affect build-up time.

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