310S Brake Systems 1 — Questions and Answers
Question 1: What is the purpose of the brake master cylinder?
- To store brake fluid for the system
- To convert mechanical force from the brake pedal into hydraulic pressure distributed to the wheel brakes (Correct answer)
- To boost the driver's braking force
- To regulate antilock brake operation
Correct answer: To convert mechanical force from the brake pedal into hydraulic pressure distributed to the wheel brakes
The master cylinder is a hydraulic pump that converts the mechanical force applied by the driver through the brake pedal into hydraulic pressure, which is transmitted through brake lines to actuate the wheel brakes.
Question 2: What does the brake pedal feel like when there is air in the hydraulic brake system?
- Hard and high
- Soft and spongy (Correct answer)
- Pulsating
- Normal with no change
Correct answer: Soft and spongy
Air in the hydraulic system is compressible, unlike brake fluid. When the pedal is applied, the air compresses before the fluid can build full pressure, resulting in a soft, spongy pedal feel.
Question 3: What is the purpose of the proportioning valve in a brake system?
- To increase front brake pressure during panic stops
- To reduce hydraulic pressure to the rear brakes to prevent premature rear wheel lockup during braking (Correct answer)
- To balance pressure between the left and right brakes
- To maintain residual pressure in the brake lines
Correct answer: To reduce hydraulic pressure to the rear brakes to prevent premature rear wheel lockup during braking
During braking, weight transfers to the front wheels, reducing rear wheel traction. The proportioning valve limits pressure to the rear brakes, preventing them from locking up before the front brakes.
Question 4: What causes brake fade during repeated hard braking?
- Low brake fluid level
- Excessive heat reducing the friction coefficient of brake pads and potentially boiling brake fluid (Correct answer)
- Worn brake pad sensors
- A failing ABS module
Correct answer: Excessive heat reducing the friction coefficient of brake pads and potentially boiling brake fluid
Repeated hard braking generates extreme heat. The brake pad friction material loses effectiveness at high temperatures, and if fluid boils, gas bubbles form in the lines creating a compressible condition, both reducing braking effectiveness.
Question 5: What is the minimum acceptable brake pad thickness for most vehicles according to Canadian standards?
- 1 mm
- 2 mm (excluding backing plate) (Correct answer)
- 4 mm
- 6 mm
Correct answer: 2 mm (excluding backing plate)
Most Canadian jurisdictions and manufacturer standards require brake pad replacement when friction material reaches 2 mm thickness (not including the metal backing plate). Some manufacturers specify 3 mm as the service limit.
Question 6: What does a pulsating brake pedal during normal braking typically indicate?
- Air in the brake lines
- Brake rotor lateral runout (thickness variation or warping) (Correct answer)
- Worn brake pad friction material
- A failing brake booster
Correct answer: Brake rotor lateral runout (thickness variation or warping)
A pulsating pedal during braking is caused by brake rotor lateral runout or thickness variation. As the rotor rotates, the thick and thin spots alternately push the caliper piston in and out, creating a pulsation felt through the pedal.
310S Brake Systems 1
What is the purpose of the brake master cylinder?