Brake Systems Flashcards
7 cards from real Automotive and Mechanics practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Brake Systems flashcards as text
Which ABS component directly modulates hydraulic brake pressure to individual wheels during an ABS-activated stop?
Answer: Hydraulic control unit (HCU) / modulator assembly
The hydraulic control unit contains solenoid valves that cycle open and closed many times per second to modulate fluid pressure at each wheel during ABS activation.
Brake rotor lateral runout (side-to-side wobble) is measured using which instrument?
Answer: Dial indicator
A dial indicator is mounted to a fixed point while the rotor is slowly rotated; the needle's total movement indicates the amount of lateral runout.
A brake caliper that seizes in the partially applied position will most likely cause which symptom?
Answer: Accelerated wear on one brake pad and excessive heat at that wheel corner
A seized caliper keeps its pad in continuous contact with the rotor, resulting in rapid uneven pad wear and dangerous heat buildup at that wheel.
Electronic Stability Control (ESC) improves vehicle stability during cornering primarily by:
Answer: Selectively applying brakes to individual wheels to correct understeer or oversteer
ESC uses yaw rate and steering angle sensors to detect loss of directional control and selectively applies one or more individual wheel brakes to steer the vehicle back on course.
A rhythmic pulsation or vibration felt through the brake pedal during braking is most often caused by:
Answer: Excessive rotor lateral runout or disc thickness variation (DTV)
Rotor lateral runout or disc thickness variation causes the caliper pistons to pump in and out as the rotor rotates unevenly, creating a pedal pulsation felt by the driver.
Brake fluid is described as hygroscopic, which means it will:
Answer: Absorb water vapor from the atmosphere over time
Hygroscopic brake fluid absorbs moisture from the air, which lowers its boiling point over time and increases the risk of vapor lock during hard or prolonged braking.
The red brake warning light on the instrument panel typically illuminates due to which of the following conditions?
Answer: Low brake fluid level, an engaged parking brake, or a hydraulic circuit fault
The red brake warning light signals safety-critical conditions: low fluid (possible leak), a parking brake left on, or a pressure imbalance between the two hydraulic circuits.