22 A5 — Brakes Practice Questions & Answers

1. 1. A driver complains that the brake pedal slowly sinks toward the floor. With the engine running, the technician applies steady, moderate foot pressure and the pedal gradually drifts down over about 15 seconds. No fluid loss is found at any wheel, at the lines, or around the master cylinder. What is the MOST LIKELY cause?

   • A.An internal (bypass) leak past the master cylinder piston cups✓ Answer
   • B.A restricted rear brake hose
   • C.Air trapped in one of the front caliper bores
   • D.A leaking vacuum booster diaphragm

   A pedal that sinks under steady pressure with no external leakage means fluid is escaping the pressure chamber internally, past worn master cylinder cups, so hydraulic volume is lost without any fluid leaving the system. Air in the system produces a spongy pedal that firms up when pumped rather than a slow steady drop, and a restricted hose or a booster fault cannot allow pedal travel while a load is being held.

   Source: ASE A5 Brakes task list, Content Area A — Master Cylinder (tasks A1–A5): diagnose pedal that slowly sinks; check master cylinder for internal/external leakageReport a problem with this question

2. 2. With the engine off, the brake pedal is pumped several times to exhaust reserve vacuum. Moderate pressure is then held on the pedal and the engine is started; the pedal drops slightly. Technician A says this proves the booster diaphragm is leaking. Technician B says this proves the booster check valve is stuck open. Who is right?

   • A.Technician A only
   • B.Technician B only
   • C.Neither Technician A nor Technician B✓ Answer
   • D.Both Technician A and Technician B

   A slight pedal drop when the engine starts is the normal, expected result of this test: engine vacuum reaches the booster and the diaphragm begins assisting, so the pedal gives way a little under the foot pressure already applied. If the pedal did not move at all, the technician would then investigate vacuum supply, the check valve, or the booster itself.

   Source: ASE A5 Brakes task list, Content Area A — Power Assist Units (tasks A19–A24): check pedal free travel with and without engine running; diagnose vacuum-type power booster operationReport a problem with this question

3. 3. A steel brake line is found rusted through in the middle of a long run under the vehicle. Which repair meets accepted service practice?

   • A.Splice in aluminum tubing and seal the joints with thread sealant
   • B.Splice in a section of soft copper tubing with single flares
   • C.Join the ends with a brass compression-fitting union
   • D.Cut out the damaged section and splice in steel brake tubing using approved fittings with double (SAE) or ISO flares✓ Answer

   Automotive hydraulic brake circuits operate at very high pressure and must use steel brake tubing sealed by a double (SAE) flare or an ISO/bubble flare, which forms a metal-to-metal seal designed for that pressure and for vibration. Compression fittings, single flares, copper and aluminum tubing are not rated for brake system pressure and can fail without warning.

   Source: ASE A5 Brakes task list, Content Area A — Brake Lines and Hoses (tasks A6–A10): replace/fabricate brake lines using proper material and double-flare and ISO flare proceduresReport a problem with this question

4. 4. After a few stops, the left front wheel of a vehicle drags heavily and the wheel is hot. When the left front caliper bleeder screw is opened, fluid squirts out and the wheel immediately turns freely. What is the MOST LIKELY cause?

   • A.A mechanically seized caliper piston
   • B.Air trapped in the left front caliper
   • C.A restricted or internally collapsed left front flexible hose acting as a one-way check valve✓ Answer
   • D.A failed rear proportioning valve

   The fact that opening the bleeder releases the drag proves pressure was trapped in the caliper rather than the piston being mechanically stuck; a deteriorated hose can pass pressure on apply but block the return flow, holding the pad against the rotor. A mechanically seized piston would not free up when the trapped pressure is vented, and air in the circuit causes a soft pedal, not a dragging brake.

   Source: ASE A5 Brakes task list, Content Area A — Brake Lines and Hoses (tasks A6–A10): diagnose poor stopping, pulling or dragging caused by brake lines and hosesReport a problem with this question

5. 5. On a vehicle with front disc and rear drum brakes, what is the function of the metering (hold-off) valve?

   • A.It senses unequal pressure between the two hydraulic circuits and turns on the red brake warning lamp
   • B.It limits pressure to the rear wheels during a hard stop to prevent rear lockup
   • C.It holds roughly 6–8 psi in the circuit so the wheel cylinder cups stay sealed
   • D.It delays pressure to the front calipers until enough pressure builds to overcome the rear shoe return springs✓ Answer

   Disc brake pads ride in light contact with the rotor and begin applying almost immediately, while drum shoes must first overcome their return springs, so the metering valve holds off front pressure briefly to let both ends start braking together. The other choices describe the proportioning valve, the residual check valve, and the pressure differential switch respectively.

   Source: ASE A5 Brakes task list, Content Area A — Valves and Switches (tasks A11–A14): inspect, test and replace metering, proportioning, pressure differential and combination valvesReport a problem with this question

6. 6. During a hard stop on dry pavement, a vehicle with front disc and rear drum brakes locks its rear wheels well before the front wheels. Tires, linings, drums and adjustment are all found to be in good condition and the vehicle is unloaded. Which component is MOST LIKELY at fault?

   • A.The proportioning valve✓ Answer
   • B.The residual check valve
   • C.The metering valve
   • D.The master cylinder reservoir cap vent

   During hard braking weight transfers forward and the rear wheels lose the traction needed to handle full line pressure, so the proportioning valve limits the rate of pressure rise to the rear circuit above a set split point; if it fails to limit that pressure the rear brakes get too much and lock early. The metering valve affects front apply timing, and the residual check valve only maintains a few psi in drum circuits.

   Source: ASE A5 Brakes task list, Content Area A — Valves and Switches (tasks A11–A14): diagnose poor stopping, pulling or dragging caused by hydraulic valvesReport a problem with this question

7. 7. Some drum brake hydraulic circuits use a residual check valve that maintains roughly 6–8 psi in the circuit at rest. Why?

   • A.It automatically compensates for lining wear as the shoes get thinner
   • B.It prevents the rear wheels from locking up before the front wheels
   • C.It holds the shoes in light contact with the drum so the brakes apply faster
   • D.The slight pressure keeps the wheel cylinder cup lips expanded against the bore so air is not drawn into the system✓ Answer

   Drum brake shoe return springs can pull fluid back fast enough to momentarily unseat the wheel cylinder cup lips, and a slight residual pressure keeps those lips sealed against the bore so air cannot be drawn past them. This is also why residual check valves are not used in disc brake circuits — any standing pressure would hold the pads against the rotor and cause drag.

   Source: ASE A5 Brakes task list, Content Area A — Valves and Switches (tasks A11–A14): inspect, test and replace hydraulic valves including residual check valvesReport a problem with this question

8. 8. This question contains the word EXCEPT. Read the question carefully before choosing your answer. All of the following statements about brake fluid are true EXCEPT:

   • A.DOT 5 silicone fluid may be added to a glycol-filled system to raise the boiling point✓ Answer
   • B.Moisture absorbed by the fluid lowers its boiling point and can cause a low or spongy pedal after repeated hard stops
   • C.DOT 3, DOT 4 and DOT 5.1 fluids are glycol based and hygroscopic, so they absorb moisture from the air over time
   • D.Petroleum-based contamination swells rubber seals and cups, so the affected rubber components must be replaced

   DOT 5 is silicone based and is not miscible with glycol fluids; mixing the two produces poor pedal feel and unpredictable performance, and DOT 5 is generally not approved for ABS-equipped vehicles. The other three statements are accurate: glycol fluids absorb moisture, the resulting lower boiling point allows the fluid to vaporize and give a low or spongy pedal after heavy use, and petroleum contamination requires replacement of the swollen rubber parts.

   Source: ASE A5 Brakes task list, Content Area A — Bleeding, Flushing, Leak Testing and Brake Fluid (tasks A15–A18): select, handle, store and install proper brake fluid, including silicone (DOT 5)Report a problem with this question

9. 9. A truck equipped with a hydro-boost power assist unit has a hard brake pedal and very little assist. Where should the technician begin diagnosis?

   • A.With the ABS hydraulic control unit and pump motor
   • B.With the master cylinder pushrod length adjustment
   • C.With the power steering system — drive belt, fluid level and condition, hoses, and pump output pressure✓ Answer
   • D.With the intake manifold vacuum supply and the booster check valve

   A hydro-boost unit is powered by pressurized fluid from the power steering pump rather than by engine vacuum, so loss of assist normally traces to low fluid, a slipping or missing belt, restricted or leaking hoses, or inadequate pump pressure. Checking manifold vacuum is meaningless on this design, which is exactly why it is used on diesel and heavy-duty applications that make little vacuum.

   Source: ASE A5 Brakes task list, Content Area A — Power Assist Units (tasks A19–A24): diagnose hydro-boost system for leaks and proper operation; refill and bleed to manufacturer specificationReport a problem with this question

10. 10. A vehicle with rear disc brakes and an electric parking brake (EPB) needs rear pads. What must the technician do before retracting the rear caliper pistons?

    • A.Compress the pistons straight in with a large C-clamp before disconnecting anything
    • B.Loosen the parking brake cable adjuster at the equalizer
    • C.Disconnect the battery negative cable to release the actuator motors
    • D.Use a scan tool to place the EPB in service/maintenance mode following the manufacturer's procedure✓ Answer

    On an EPB the caliper piston is driven by an electric actuator through a screw mechanism, so it must be commanded back electronically in service mode; forcing it in with a clamp can destroy the actuator gearset and the piston screw. The same principle applies to conventional integral parking brake calipers, where the piston must be screwed in with the correct tool rather than pushed straight in.

    Source: ASE A5 Brakes task list, Content Area A — Parking Brake including Electronic Parking Brake (tasks A25–A29): retract integral and/or electronic parking brake caliper pistons per manufacturer procedureReport a problem with this question

11. 11. A vehicle with rear duo-servo drum brakes has a low brake pedal that comes up when pumped. The fluid level is correct, there are no leaks and the pedal is firm once pumped. The owner says the vehicle is almost never backed up. What is the MOST LIKELY cause?

    • A.The rear brake linings are contaminated with grease
    • B.A rear wheel cylinder is leaking internally past its cups
    • C.The rear shoes are far out of adjustment because the self-adjusters are not working✓ Answer
    • D.The master cylinder has an internal bypass leak

    Excessive shoe-to-drum clearance means the first pedal stroke is used up taking up that clearance, and pumping stores the shoes closer to the drum so the pedal comes up and feels firm. On most duo-servo designs the star-wheel self-adjuster indexes during reverse stops, so a vehicle that is rarely backed up with the brakes applied will fall out of adjustment; a master cylinder bypass leak would give a pedal that sinks under steady pressure instead.

    Source: ASE A5 Brakes task list, Content Area B — Drum Brake Diagnosis and Repair: diagnose incorrect pedal travel; inspect, service and test self-adjuster mechanismsReport a problem with this question

12. 12. A drum brake assembly is heavily coated with brake dust. What is the correct way to clean it?

    • A.Spray the assembly with solvent and let the runoff go to the shop floor
    • B.Use a HEPA-filtered vacuum enclosure or an approved wet-cleaning method that captures the residue✓ Answer
    • C.Blow the dust off with shop compressed air while wearing a dust mask
    • D.Brush the dust off dry and wipe the parts with a shop rag

    Brake dust can contain asbestos and other respirable particulate, and any dry method — compressed air, dry brushing or wiping — puts those particles into the technician's breathing zone and into the shop air. HEPA vacuum enclosures and wet cleaning keep the residue captured so it can be disposed of properly.

    Source: ASE A5 Brakes task list, Content Area B — Drum Brake Diagnosis and Repair (task B5): clean and inspect brake drum assembly using approved dust-control proceduresReport a problem with this question

13. 13. A dial indicator is clamped rigidly to the suspension with its plunger contacting the rotor face about a half inch in from the outer edge. The rotor is turned one full revolution and the total sweep of the needle is recorded. What is being measured?

    • A.Brake pad taper wear
    • B.Rotor thickness variation (parallelism)
    • C.Rotor lateral runout✓ Answer
    • D.Rotor minimum (discard) thickness

    A dial indicator reading taken against the face of a rotating rotor shows how far the braking surface moves side to side as it turns, which is lateral runout, and excessive runout produces pedal pulsation and in time wears the rotor into thickness variation. Thickness and thickness variation cannot be read this way because they require a micrometer measuring across both faces.

    Source: ASE A5 Brakes task list, Content Area C — Disc Brake Diagnosis and Repair: measure rotor lateral runout with a dial indicator per manufacturer procedureReport a problem with this question

14. 14. After machining, a brake rotor measures thinner than the minimum (discard) thickness cast into it. What is the correct course of action?

    • A.Replace the rotor✓ Answer
    • B.Machine the opposite rotor to the same thickness so the axle is matched
    • C.Return it to service after applying a non-directional finish
    • D.Install it with thicker replacement pads to make up the difference

    Minimum thickness is the point below which the rotor can no longer absorb and dissipate braking heat safely and loses the strength to resist cracking and distortion, so a rotor at or below it must be replaced. A non-directional finish, matching the other side, or thicker pads do nothing to restore the missing mass, and the separate machine-to specification is deliberately thicker than discard so a machined rotor still has material left for one pad life.

    Source: ASE A5 Brakes task list, Content Area C — Disc Brake Diagnosis and Repair: measure rotor thickness and compare to minimum (discard) specification; replace rotors below specificationReport a problem with this question

15. 15. A floating (sliding) caliper is removed and the inboard pad is worn nearly to the backing plate while the outboard pad still has most of its friction material. Technician A says excessive rotor lateral runout caused this wear pattern. Technician B says air trapped in the caliper caused it. Who is right?

    • A.Neither Technician A nor Technician B✓ Answer
    • B.Technician A only
    • C.Both Technician A and Technician B
    • D.Technician B only

    Wear concentrated on the piston side points to a caliper piston that is not releasing and holds the inboard pad against the rotor after the pedal is released; seized slide pins or bushings are the other common cause of side-to-side uneven wear. Lateral runout wears both pads and shows up as pulsation, and air in the caliper only affects pedal feel, so neither technician is correct.

    Source: ASE A5 Brakes task list, Content Area C — Disc Brake Diagnosis and Repair: diagnose pad wear patterns; inspect caliper piston, seals, mounting hardware and slidesReport a problem with this question

16. 16. A customer reports the brake pedal pulsing up and down and a shudder in the steering wheel, but only while braking from highway speed. The technician uses a micrometer to measure rotor thickness at several evenly spaced points around the rotor at the same radius. What condition is being checked, and why does it cause the complaint?

    • A.Disc thickness variation, because the thick and thin spots push the caliper piston in and out once per revolution✓ Answer
    • B.Lateral runout, because the indicator plunger follows the wobble of the braking surface
    • C.Minimum thickness, because a thin rotor flexes under caliper clamping force
    • D.Rotor hardness, because hard spots resist the friction material differently

    Measuring across both faces with a micrometer at points around the same radius reveals disc thickness variation, and each thick spot passing between the pads forces the piston back and pushes a pressure pulse up the line to the pedal, felt as pulsation and shudder. Lateral runout requires a dial indicator instead, and it typically causes thickness variation over time rather than being what the micrometer reads.

    Source: ASE A5 Brakes task list, Content Area C — Disc Brake Diagnosis and Repair: measure rotor thickness variation (parallelism) with a micrometer; diagnose pedal pulsationReport a problem with this question

17. 17. A vehicle has a rumbling, growling noise that rises with vehicle speed, is present whether or not the brakes are applied, and changes in loudness when the vehicle is swerved gently left and right. What is the MOST LIKELY cause?

    • A.A worn wheel bearing✓ Answer
    • B.A sticking caliper slide pin
    • C.A warped brake rotor
    • D.Glazed brake pads

    Swerving transfers vehicle weight from one side to the other and changes the load on each wheel bearing, so a noise that gets louder or quieter with that weight shift and exists with the brakes released is a bearing, not a brake, complaint. Brake-related noise and vibration appear or change when the pedal is applied; note also that many sealed hub/bearing assemblies are non-serviceable and often carry the ABS tone ring and wheel speed sensor, so they are replaced as a unit.

    Source: ASE A5 Brakes task list, wheel bearing tasks under Content Areas B and C: diagnose wheel bearing noise; inspect and replace wheel bearing/hub assembliesReport a problem with this question

18. 18. On dry pavement during a light, normal stop, ABS activates briefly just as the vehicle slows to a walking pace. The amber ABS lamp comes on and a wheel speed sensor circuit code is stored; base braking is otherwise normal. What is the MOST LIKELY cause?

    • A.Worn brake pads at one front wheel
    • B.A failed proportioning valve
    • C.A damaged or debris-packed tone (reluctor) ring at one wheel producing an erratic speed signal✓ Answer
    • D.A low brake fluid level in the master cylinder reservoir

    The control module compares all four wheel speed signals, so a chipped, cracked or debris-packed tone ring makes one wheel appear to decelerate or stop suddenly and the module reacts by releasing pressure at that wheel — classic false low-speed activation. Low fluid or a valve fault would set base-system symptoms and the red brake lamp rather than a wheel speed sensor code.

    Source: ASE A5 Brakes task list, Content Area D — Electronic Brake Control Systems: inspect wheel speed sensors, tone/reluctor rings, air gap and circuits; diagnose false ABS activationReport a problem with this question

19. 19. During a hard stop on wet pavement the driver feels rapid pulsation in the brake pedal, hears clicking from the wheels and a motor buzzing under the hood, and the vehicle stops under control with no warning lamps on. What should the technician tell the customer?

    • A.The brake pads are worn out and the wear sensors are contacting the rotors
    • B.This is normal ABS operation as the system cycles pressure to prevent wheel lockup✓ Answer
    • C.There is air in the hydraulic system and it needs to be bled
    • D.The hydraulic control unit is failing and must be replaced

    When ABS activates, the modulator solenoids open and close and the pump motor runs to restore pressure, and that mechanical action is transmitted back through the fluid as pedal pulsation along with clicking and buzzing noises. Because no lamps are on and the vehicle stopped under control, the system performed as designed; ABS is there to preserve steering control during hard braking, and it does not always shorten stopping distance.

    Source: ASE A5 Brakes task list, Content Area D — Electronic Brake Control Systems: identify and interpret normal electronic brake control system operation and noisesReport a problem with this question

20. 20. How does a passive (variable-reluctance) wheel speed sensor differ from an active (Hall-effect or magnetoresistive) wheel speed sensor?

    • A.The passive sensor needs a supply voltage while the active sensor generates its own AC signal
    • B.The passive sensor reads brake pressure while the active sensor reads wheel speed
    • C.Both types generate their own signal, but only the active type can be tested with a lab scope
    • D.The passive sensor generates its own AC signal whose amplitude and frequency rise with speed and is unusable near zero mph, while the active sensor needs a supply voltage and gives a usable digital signal down to nearly zero mph✓ Answer

    A passive sensor is a coil and magnet that induces voltage only when tone ring teeth move past it, so its output weakens and disappears as the wheel nearly stops and it is checked with resistance, AC voltage and a scope waveform. An active sensor is powered by the module and switches a digital or current-modulated output, which is why systems that need low-speed data such as traction control and stability control use them.

    Source: ASE A5 Brakes task list, Content Area D — Electronic Brake Control Systems: test, diagnose and service wheel speed sensors and circuits (passive and active types)Report a problem with this question

21. 21. The amber ABS warning lamp comes on at start-up and stays on. The red BRAKE lamp is off, pedal height and feel are normal, and the vehicle stops straight. Which statement is correct?

    • A.The base hydraulic brakes still work, but ABS and related functions are disabled until the stored codes are diagnosed and repaired✓ Answer
    • B.This is the normal ABS self-test and no service is needed
    • C.The red lamp is the ABS lamp, so the amber lamp indicates only low washer fluid
    • D.The vehicle has no braking capability and must not be moved

    The amber lamp is the ABS lamp and it means the module has set a fault and shut the antilock function off, leaving the conventional hydraulic brakes to operate normally; the red lamp is reserved for base-system problems such as low fluid, a pressure differential or an applied parking brake. A brief amber lamp at start-up that goes out is the normal self-test, but a lamp that stays on calls for retrieving and diagnosing the stored codes with a scan tool.

    Source: ASE A5 Brakes task list, Content Area D — Electronic Brake Control Systems: interpret electronic brake control system warning lamp operation and retrieve diagnostic trouble codesReport a problem with this question

22. 22. Following a four-wheel alignment and replacement of a steering linkage component, the stability control (ESC) lamp is on and a steering angle sensor code is stored. Mechanical inspection finds nothing wrong. What is MOST LIKELY required?

    • A.The brake hydraulic system must be bled with a scan tool
    • B.The steering angle sensor must be replaced
    • C.The steering angle sensor must be recalibrated (zeroed) using the manufacturer's procedure✓ Answer
    • D.The clockspring must be replaced

    Stability control compares where the driver is steering with the yaw rate and lateral acceleration the vehicle is actually producing, so the module must know true straight-ahead; alignment, steering, suspension or column work changes that reference and requires the sensor to be relearned. Replacing hardware that is not faulty will not clear the code, because the stored value, not the sensor, is what is wrong.

    Source: ASE A5 Brakes task list, Content Area D — Electronic Brake Control Systems: describe the operation of steering angle, yaw rate and lateral accelerometer sensors; perform required set-up, initialization and calibration proceduresReport a problem with this question

Practice questions written to the ASE Automobile & Light Truck (A-series) task lists and standard automotive service principles. ASE is a mark of the National Institute for Automotive Service Excellence; this site is not affiliated with or endorsed by ASE. Always follow the vehicle manufacturer's service information for specifications and procedures on a real repair. About the ASE tests →