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SOS Mechanic Certification- Brakes Exam Questions
with correct Answers plus Rationales
This practice set covers hydraulic systems, disc and drum brakes, parking brakes, power assist systems, and electronic brake controls.
1. What is the primary function of a master cylinder in a hydraulic brake system? A. Increase brake pad life B. Store brake fluid C. Generate hydraulic pressure D. Lubricate brake lines The master cylinder converts mechanical force from the brake pedal into hydraulic pressure used to apply the brakes. 2. Which of the following is a symptom of a failing brake booster? A. Low brake fluid B. Hard brake pedal C. Squealing brakes D. Uneven tire wear A faulty brake booster will result in a hard brake pedal due to loss of vacuum assist. 3. What component maintains residual pressure in drum brake systems? A. Brake caliper
B. Residual check valve C. Brake pad D. Brake booster The residual check valve maintains slight pressure in drum systems to keep shoes close to the drum.
4. What type of brake system uses friction between a rotor and pads? A. Disc brake B. Drum brake C. Parking brake D. Power brake Disc brakes use pads to clamp a rotor, generating friction to stop the vehicle. 5. Which tool is used to measure brake rotor thickness? A. Micrometer B. Vernier caliper C. Dial indicator D. Torque wrench A vernier caliper accurately measures rotor thickness to assess wear or warping. 6. What is the most likely cause of brake pull during braking? A. Failing brake light switch B. Uneven pad wear or stuck caliper C. Low power steering fluid D. Bad master cylinder Uneven braking force from a stuck caliper or worn pad can cause the car to pull to one side.
D. Sticking ignition switch Brake fade occurs when components overheat and lose friction efficiency.
11. What is the function of the proportioning valve? A. Directs fluid only to rear brakes B. Balances pressure between front and rear brakes C. Engages ABS D. Regulates brake fluid temperature The proportioning valve adjusts pressure to prevent rear wheel lock-up. 12. What causes a grinding noise when braking? A. Metal-to-metal contact from worn pads B. Low transmission fluid C. Broken return spring D. Water in brake fluid Worn-out pads lead to metal contact between backing plate and rotor, causing grinding. 13. What is the most common symptom of a warped rotor? A. Brake warning light B. Pulsation during braking C. Low pedal height D. Hissing noise Warped rotors cause the brake pedal to pulsate as it contacts the uneven rotor surface. 14. Which type of brake uses hydraulic pressure directly on pistons inside a caliper?
A. Disc brake B. Drum brake C. Parking brake D. ABS brake Disc brakes apply fluid pressure to caliper pistons, squeezing pads against the rotor.
15. Which of the following is a safety feature of dual-circuit master cylinders? A. Reduces fluid temperature B. Provides backup in case of failure C. Helps adjust pedal height D. Controls ABS Dual-circuit systems provide redundancy; if one circuit fails, the other still functions. 16. What is the purpose of bleeding brakes? A. Lubricate the calipers B. Remove air from hydraulic lines C. Adjust the booster D. Replace the brake fluid Bleeding eliminates trapped air that can compromise hydraulic pressure. 17. Which condition indicates the need to resurface or replace a rotor? A. Brake fluid contamination B. Excessive thickness variation C. Rear brake lock-up D. Low pad thickness
(Questions 21–50 continue in next message for spacing clarity...) SOS Mechanic Certification – Brakes Exam (Continued: Questions 21–50) Correct answers are bolded; rationales are in bold italics
21. What component activates the brake lights when the brake pedal is pressed? A. Wheel cylinder B. Brake light switch C. Booster check valve D. Proportioning valve The brake light switch completes the electrical circuit to turn on brake lights when the pedal is pressed. 22. What is a typical symptom of contaminated brake fluid? A. Grinding noise B. Pulsation during braking C. Spongy pedal feel D. High brake pedal Water or air contamination lowers the boiling point and compressibility, causing a spongy pedal. 23. Which type of brake system uses leading and trailing shoes? A. Disc brake B. Drum brake C. ABS brake
D. Power brake Drum brakes use shoes that are either leading (primary) or trailing (secondary).
24. A vehicle pulls left when braking. What is the likely cause? A. Frozen right caliper B. Frozen left caliper C. Warped steering knuckle D. Low coolant A stuck right caliper would reduce braking force on that side, causing a pull to the left. 25. Which component is responsible for maintaining proper brake pad alignment in a disc system? A. Proportioning valve B. Caliper guide pins C. Master cylinder D. Return spring Guide pins ensure the caliper moves evenly and keeps pads parallel to the rotor. 26. What could happen if a vehicle’s brake fluid is not replaced regularly? A. Moisture contamination leads to corrosion B. Tires wear faster C. Pedal height increases D. Calipers stick permanently Brake fluid absorbs moisture, which lowers boiling point and causes corrosion. 27. What test is performed to determine if a brake booster is functioning properly?
31. Which tool checks brake rotor lateral runout? A. Dial indicator B. Feeler gauge C. Vernier caliper D. Torque wrench A dial indicator detects rotor side-to-side movement or wobble. 32. If a rotor is below minimum thickness, what must be done? A. Machine it B. Replace it C. Clean it D. Bleed the brakes Rotors below minimum are unsafe and must be replaced, not machined. 33. Which part helps maintain equal hydraulic pressure to both front wheels? A. Brake pads B. Parking brake C. Master cylinder D. Dust boots The master cylinder evenly distributes hydraulic force to each side. 34. Which part applies hydraulic pressure to brake shoes in drum brakes? A. Adjuster screw B. Wheel cylinder C. Return spring D. Anchor pin Wheel cylinders use pistons to press the shoes outward against the drum.
35. Which issue would most likely trigger the ABS warning light? A. Low coolant B. Damaged wheel speed sensor C. Dirty air filter D. Low engine oil ABS relies on wheel speed sensors; damage or failure triggers the ABS warning. 36. Which is NOT a reason for brake drag? A. Misadjusted parking brake B. Stuck caliper C. Swollen rubber hose D. Worn-out pads Worn pads do not cause drag; they simply reduce braking efficiency. 37. Which type of brake fluid should not be mixed with DOT 3 or DOT 4? A. DOT 3 B. DOT 5 C. DOT 4 D. DOT 3 Synthetic DOT 5 is silicone-based and incompatible with glycol-based DOT 3/4. 38. Which action helps eliminate uneven brake pad wear? A. Lubricate caliper slides B. Change brake light fuse C. Lower fluid level D. Flush transmission Caliper slides must move freely to ensure even wear on both pads.
D. Flush them with DOT 5 Pads won’t fit unless the pistons are fully retracted to accommodate new thickness.
43. Which system modulates hydraulic pressure to avoid wheel lock-up? A. Master cylinder B. Booster C. ABS controller D. Parking brake lever The ABS controller rapidly modulates hydraulic pressure to prevent skidding. 44. If brake shoes are soaked with brake fluid, what should be done? A. Clean them B. Replace them C. Heat them to dry D. Sand them Fluid-contaminated shoes lose friction and must be replaced. 45. Which component amplifies brake pedal force? A. Wheel cylinder B. Rotor C. Brake booster D. Star adjuster The booster uses vacuum (or hydraulic assist) to multiply pedal force. 46. What does a dragging brake typically cause? A. Improved fuel economy B. Brighter brake lights
C. Overheating and premature wear D. Higher pedal Dragging brakes generate excess heat and wear components faster.
47. Which symptom is most likely from a seized caliper piston? A. Vehicle pulling during braking B. Squeaking suspension C. Blinking ABS light D. Delayed engine start A seized piston creates unequal braking force, leading to pulling. 48. When is the parking brake typically applied in drum brakes? A. When the lever or pedal is actuated B. When ABS activates C. During shifting D. When turning The parking brake pulls cables that force shoes outward manually. 49. A spongy pedal after pad replacement usually indicates: A. Faulty ABS B. Air in brake lines C. Sticky master cylinder D. Warped rotor Air may have entered the system during pad replacement; bleeding is required. 50. What is the first step when replacing disc brake pads? A. Remove rotors B. Disconnect battery
The metering valve holds pressure to delay front disc brake engagement until rear drums apply.
54. What’s the purpose of the anti-rattle clips in disc brakes? A. Increase brake force B. Provide cooling C. Reduce pad noise and movement D. Engage the ABS Anti-rattle clips secure the pads and minimize noise or vibration. 55. A brake pad wear sensor usually triggers what kind of warning? A. Check engine B. Low oil C. Brake warning light D. Tire pressure Wear sensors complete a circuit when pads wear down, triggering a brake warning. 56. What component is adjusted using a brake spoon? A. Caliper piston B. Drum brake star adjuster C. Booster pushrod D. Master cylinder bore A brake spoon fits into the access hole to turn the star wheel adjuster. 57. Why is it important to torque lug nuts properly after brake service? A. Prevent pad wear B. Boost engine RPM
C. Avoid rotor warping D. Improve tire balance Uneven lug nut torque can warp the brake rotor due to uneven clamping force.
58. What is the effect of a collapsed brake hose? A. Increased brake fluid B. Booster failure C. Caliper stays engaged D. Rear brake lockup A collapsed hose can restrict fluid return, keeping the caliper pressurized and engaged. 59. Why are dual diagonal brake systems used? A. Lower cost B. Maintain braking if one circuit fails C. Reduce ABS weight D. Simplify repair These systems enhance safety by allowing some braking power even if one hydraulic circuit fails. 60. Which brake system component typically contains a vent port and compensation port? A. ABS control module B. Proportioning valve C. Master cylinder D. Wheel cylinder
C. Retract piston using a screw-type tool D. Bleed the booster These systems use threaded pistons that must be rotated as they’re pushed back.
65. The wear indicator on a drum brake shoe typically contacts the: A. Caliper B. Brake drum C. Wheel bearing D. Shoe anchor The wear indicator contacts the drum to produce a squeal when shoes are worn. 66. Which of the following requires a scan tool to reset or initialize? A. Drum brake shoe replacement B. Electronic parking brake C. Manual brake bleeding D. Wheel cylinder installation Electronic parking brakes often require a scan tool to retract pistons or reset codes. 67. What is a common sign of excessive rotor thickness variation? A. ABS light B. Grinding sound C. Pedal pulsation during braking D. Clicking when turning Uneven rotor thickness causes pedal pulsation as pads encounter high and low spots.
68. What is the usual brake pedal response when the engine is off? A. Hard and high B. Low and spongy C. Sinks slowly D. Pulsates With the engine off, there’s no vacuum assist, resulting in a firm, hard pedal. 69. What happens when the ABS control module detects rapid deceleration at one wheel? A. Disables the system B. Activates brake booster C. Pulses brake pressure to that wheel D. Shuts off fuel pump ABS modulates pressure to prevent lock-up and maintain traction. 70. What is the function of the brake backing plate in a drum brake system? A. Adjust fluid level B. Vent brake heat C. Provide support for brake components D. Lubricate shoes The backing plate anchors springs, shoes, and other drum brake parts. 71. Which component stores hydraulic pressure in a hybrid braking system? A. Proportioning valve B. Brake pedal sensor C. Accumulator D. Master cylinder
