Automotive and Mechanics Brake Systems 1 — Questions and Answers
Question 1: What type of brake fluid is most commonly specified for standard passenger vehicles in the United States?
- DOT 5 (silicone-based)
- DOT 1 (outdated standard)
- DOT 3 (glycol-based) (Correct answer)
- DOT 6 (racing-grade)
Correct answer: DOT 3 (glycol-based)
DOT 3 is the most widely specified glycol-based brake fluid for standard passenger vehicles and meets FMVSS 116 requirements.
Question 2: What is the primary function of the master cylinder in a hydraulic brake system?
- Store reserve brake fluid
- Convert mechanical pedal force into hydraulic pressure (Correct answer)
- Distribute pressure equally to all four wheels
- Amplify braking force using engine vacuum
Correct answer: Convert mechanical pedal force into hydraulic pressure
The master cylinder converts the mechanical force applied to the brake pedal into hydraulic pressure that travels through the lines to actuate the brakes.
Question 3: Which type of brake assembly uses calipers that squeeze pads against a rotating disc to slow the vehicle?
- Drum brake
- Band brake
- Disc brake (Correct answer)
- Regenerative brake
Correct answer: Disc brake
Disc brakes use a caliper that clamps brake pads against a flat rotating rotor (disc), generating friction to decelerate the wheel.
Question 4: What does the abbreviation ABS stand for in automotive brake terminology?
- Automatic Brake Stabilizer
- Advanced Braking Sensor
- Axle Balance System
- Anti-lock Braking System (Correct answer)
Correct answer: Anti-lock Braking System
ABS (Anti-lock Braking System) prevents wheel lockup during hard braking by rapidly modulating hydraulic pressure at each wheel.
Question 5: At what minimum remaining thickness (mm) should disc brake pads typically be replaced?
- 1 mm
- 3 mm (Correct answer)
- 5 mm
- 8 mm
Correct answer: 3 mm
Brake pads should be replaced at approximately 3 mm (about 1/8 inch) of remaining friction material to maintain safe stopping performance.
Question 6: What is the primary purpose of a brake proportioning valve in a vehicle's brake system?
- Increase hydraulic pressure to the front brakes
- Equalize pressure across all brake circuits
- Limit hydraulic pressure to the rear brakes to prevent rear-wheel lockup (Correct answer)
- Activate the ABS module during emergency stops
Correct answer: Limit hydraulic pressure to the rear brakes to prevent rear-wheel lockup
The proportioning valve limits rear brake pressure relative to front pressure so the lighter rear end does not lock up first, which could cause a spin.
Question 7: The term 'brake fade' describes which condition?
- Gradual wear of brake pad friction material over time
- Discoloration of brake rotors caused by heat
- A loss of braking effectiveness caused by overheated brakes (Correct answer)
- A slow decrease in brake fluid reservoir level
Correct answer: A loss of braking effectiveness caused by overheated brakes
Brake fade occurs when brake components overheat, causing reduced friction coefficient and significantly longer stopping distances.
