ASE A5 Brakes Certification Test — Questions and Answers

Question 1: Which of the following is a safe fluid to use for cleaning hydraulic brake components such as a master cylinder bore or caliper pistons during service?

Penetrating oil spray
Engine oil
Mineral spirits
Denatured alcohol or clean brake fluid (Correct answer)

Correct answer: Denatured alcohol or clean brake fluid

Denatured alcohol and clean brake fluid will not harm rubber seals. Petroleum products cause the rubber to swell and fail.

Question 2: A technician is replacing a section of steel brake line on a vehicle that uses SAE 45-degree flare fittings. Which type of flare should be formed on the tube end?

A beaded flare with no fitting nut
A flat-ended compression flare
A double flare (Correct answer)
A single flare, because it seals best against the seat

Correct answer: A double flare

SAE 45-degree brake fittings require a double flare. The doubled-over wall is stronger and resists splitting under high pressure.

Question 3: A technician finds brake fluid on the firewall and inside the vacuum booster behind the master cylinder, and the reservoir level keeps falling. What is the most likely cause?

A faulty brake light switch
A leaking front brake caliper piston seal
A leaking rear (primary piston) seal in the master cylinder (Correct answer)
A cracked brake hose at the rear axle

Correct answer: A leaking rear (primary piston) seal in the master cylinder

Fluid at the booster and firewall points to the master cylinder's primary piston rear seal leaking out of the back of the bore.

Question 4: Before disconnecting a brake line on an integral ABS with a high-pressure accumulator, what must be done first to relieve stored pressure?

Disconnect the wheel speed sensors and drive the vehicle (Correct answer)
Turn the ignition on and hold the pedal down for 10 seconds
Open all four bleeder screws while the pump motor is running
With the ignition off, pump the brake pedal many times until it feels hard

Correct answer: Disconnect the wheel speed sensors and drive the vehicle

Accumulator pressure can reach roughly 2,000 psi or more. It is relieved by pumping the pedal with the ignition off until the pedal becomes firm.

Question 5: A technician measures a brake drum and finds the friction surface is larger than the maximum diameter cast into the drum. What is the correct action?

Install thicker linings to compensate
Reuse the drum if it has no hard spots
Replace the drum (Correct answer)
Machine the drum lightly to true the surface

Correct answer: Replace the drum

The cast discard diameter is the largest safe inside diameter. A drum beyond it has less metal to absorb heat and resist cracking, so it must be replaced.

Question 6: Before measuring lateral runout of a front disc brake rotor with a dial indicator, what should the technician do first?

Make sure the wheel bearing has no excess play and the rotor is mounted correctly (Correct answer)
Remove the brake pads and clean the pad area
Lubricate the caliper slide pins
Bleed the brakes to remove all air

Correct answer: Make sure the wheel bearing has no excess play and the rotor is mounted correctly

Looseness in the wheel bearing or poor rotor mounting can give a false runout reading. The bearing and rotor mounting must be correct before measuring.

Question 7: A technician is pressure bleeding a brake system. Which of the following is the correct practice?

Pressurize the system to about 15 psi using an adapter that fits the master cylinder reservoir (Correct answer)
Pressurize the reservoir with shop air directly, without a diaphragm tank
Remove the reservoir cap and hold the pedal down with a block of wood
Pressurize the system to about 100 psi to speed the process

Correct answer: Pressurize the system to about 15 psi using an adapter that fits the master cylinder reservoir

Pressure bleeders typically run at roughly 10–25 psi through a proper reservoir adapter. Higher pressure risks damaging seals and the reservoir.

Question 8: A vehicle's brake pedal slowly sinks toward the floor while steady pressure is held. There are no external leaks and the reservoir level has not dropped. What is the most likely cause?

A glazed brake rotor surface
A restricted brake hose at the left front wheel
A seized rear caliper piston
Worn or damaged piston cups inside the master cylinder bore (Correct answer)

Correct answer: Worn or damaged piston cups inside the master cylinder bore

A pedal that sinks with no external leak and no fluid loss points to fluid bypassing the master cylinder piston cups internally.

Question 9: A technician needs to loosen a corroded brake line fitting at a wheel cylinder. Which tool is the best choice to reduce the risk of rounding the fitting?

Locking pliers
Adjustable wrench
Open-end wrench
Flare-nut (line) wrench (Correct answer)

Correct answer: Flare-nut (line) wrench

A flare-nut wrench grips most of the fitting's flats, which spreads force and helps prevent rounding the soft fitting nut.

Question 10: A technician has just installed a new master cylinder. What should be done before it is connected to the brake lines?

Apply a light coat of grease to the piston bores to help the seals slide
Fill the reservoir with fluid and pump the pedal until firm after the lines are attached
Back off the pushrod adjustment fully so the pistons stay retracted
Bench bleed the master cylinder to remove air from its bores and outlet ports (Correct answer)

Correct answer: Bench bleed the master cylinder to remove air from its bores and outlet ports

Bench bleeding removes air trapped in the master cylinder bores before installation, making the later system bleed much easier.

Question 11: A customer complains of a pulsating brake pedal and a buzzing noise during a panic stop on loose gravel. The ABS warning light stays off and no codes are stored. What should the technician conclude?

The ABS pump motor is failing and the modulator must be replaced
The ABS is operating normally and the pedal pulsation is expected (Correct answer)
The wheel speed sensors are out of range and must be adjusted
The front rotors are warped and need to be replaced

Correct answer: The ABS is operating normally and the pedal pulsation is expected

During ABS activation the modulator rapidly cycles its valves and pump, which produces pedal pulsation and noise. Low-traction surfaces trigger ABS easily.

Question 12: After a brake job, a customer reports squeaking from a rear drum brake during light braking. The linings and drum are new. Which service step was most likely missed?

Tightening the star-wheel adjuster until the drum drags
Machining the drum to a mirror finish
Applying high-temperature brake lubricant to the backing plate shoe contact points (Correct answer)
Coating the lining surface with brake grease

Correct answer: Applying high-temperature brake lubricant to the backing plate shoe contact points

The shoe edges slide on raised pads on the backing plate. When those contact points are dry or rusty, the shoes stick and chatter, which causes noise. A thin film of high-temperature brake lubricant fixes this.

Question 13: A pickup with a height-sensing proportioning valve has its rear wheels lock up early under hard braking when the truck is lightly loaded. Which is the most likely cause?

A seized valve linkage or a misadjusted valve that holds it in the loaded position (Correct answer)
A leaking primary piston seal in the master cylinder
A failed pressure differential switch
Worn rear brake shoe linings

Correct answer: A seized valve linkage or a misadjusted valve that holds it in the loaded position

A height-sensing valve should reduce rear pressure when the vehicle is lightly loaded. If the linkage is stuck or misadjusted as if loaded, rear pressure stays too high and the rear wheels lock early.

Question 14: A technician finds a brake hose that appears swollen along part of its length when the brake pedal is firmly applied. What action is correct?

Tighten the hose end fitting a quarter turn
Replace the hose (Correct answer)
Bleed the line until the bulge disappears
Wrap the area with tape and recheck in a month

Correct answer: Replace the hose

A bulge means the reinforcing layers have failed and the hose could burst. The hose must be replaced.

Question 15: Why is copper tubing not acceptable for replacing a steel brake line?

It expands too much when heated by the brakes
It reacts chemically with DOT 3 brake fluid
It cannot be flared with standard tools
It work-hardens and cracks from vibration, and it cannot safely withstand brake system pressures (Correct answer)

Correct answer: It work-hardens and cracks from vibration, and it cannot safely withstand brake system pressures

Copper work-hardens with vibration and flexing, which leads to cracking and leaks. It also lacks the strength needed for brake pressures.

Question 16: An ABS warning light comes on only above about 25 mph, and a wheel speed sensor circuit code sets intermittently. The sensor resistance and wiring test good. Which is the most likely cause?

A low brake fluid level in the master cylinder reservoir
A worn brake pad on the same wheel
A cracked or damaged tone ring or debris packed on its teeth (Correct answer)
A weak rear shock absorber on the opposite side

Correct answer: A cracked or damaged tone ring or debris packed on its teeth

A damaged, corroded or contaminated tone ring causes dropouts in the signal that appear only at certain speeds, even when the sensor itself tests good.

Question 17: To test a vacuum brake booster, a technician pumps the pedal several times with the engine off, holds firm pressure, and starts the engine. What should happen if the booster and vacuum supply are working properly?

The pedal should not move at all
The pedal should drop slightly under steady pressure (Correct answer)
The pedal should pulsate rapidly
The pedal should push back up against the foot

Correct answer: The pedal should drop slightly under steady pressure

When engine vacuum reaches the booster, the pedal drops a little as the booster provides assist.

Question 18: During a master cylinder replacement, the pushrod is adjusted too long so that it holds the primary piston forward with the pedal released. Which symptom is most likely?

Excessive brake pedal travel before the brakes apply
A brake warning lamp that stays off during a circuit failure
Brakes that drag and overheat because the compensating port stays covered (Correct answer)
A hard pedal with the engine running

Correct answer: Brakes that drag and overheat because the compensating port stays covered

A pushrod that is too long keeps the primary cup over the compensating port, so pressure cannot release and the brakes drag.

Question 19: A technician finds that a master cylinder's rubber cups are swollen and the fluid looks contaminated with petroleum-based oil. What is the correct repair?

Add DOT 5 fluid to dilute the contamination
Bleed the system at each wheel until the fluid looks clear
Replace the master cylinder only and refill with fresh fluid
Flush the system and replace the master cylinder, all rubber hoses and seals, and other contaminated components (Correct answer)

Correct answer: Flush the system and replace the master cylinder, all rubber hoses and seals, and other contaminated components

Petroleum oil swells rubber seals and hoses throughout the hydraulic system, so all affected rubber parts must be replaced and the system flushed.

Question 20: On a vehicle with ABS, air remains in the hydraulic control unit after the wheel circuits have been conventionally bled, and the pedal is still soft. What is the best next step?

Use a scan tool to run the ABS automated bleed procedure, which cycles the valves and pump, and then bleed the wheels again (Correct answer)
Replace the ABS wheel speed sensors
Remove the hydraulic unit and bleed it on the bench
Disconnect the ABS fuse and bleed the wheels again with the ignition on

Correct answer: Use a scan tool to run the ABS automated bleed procedure, which cycles the valves and pump, and then bleed the wheels again

Many ABS units hold air in internal passages that conventional bleeding cannot reach. A scan tool bleed cycles the valves and pump so the air can be pushed out.

Question 21: A vehicle has an electro-mechanical brake booster that uses an electric motor instead of vacuum. The driver reports a hard pedal and a brake warning light. What should the technician do first?

Replace the vacuum check valve
Retrieve diagnostic trouble codes and check power and ground supply (Correct answer)
Install a new master cylinder immediately
Bleed the booster with a vacuum pump

Correct answer: Retrieve diagnostic trouble codes and check power and ground supply

Electric boosters are controlled by a module and depend on proper voltage and ground, so scanning for codes and checking electrical supply is the correct starting point.

Question 22: A vehicle has a steering wheel and brake pedal pulsation that appears only during braking and gets worse at highway speeds. The pads and fluid are normal. Which condition is the most likely cause?

A restricted rear brake hose
Air in the hydraulic system
Disc thickness variation from rotor runout (Correct answer)
Weak brake booster vacuum supply

Correct answer: Disc thickness variation from rotor runout

Rotor thickness variation makes the pads push back and forth as the rotor turns. This shows up as a pulsing pedal and, on front brakes, steering wheel shake.

Question 23: A vehicle pulls to the right whenever the brakes are applied. The brake pedal feels normal and there is no noise. Which condition is the most likely cause?

Brake fluid contamination on the right front pads
A seized caliper piston on the left front brake (Correct answer)
Glazed pads on the right front brake
A weak return spring on the right rear shoe

Correct answer: A seized caliper piston on the left front brake

A vehicle pulls toward the side with more braking force. A seized left caliper piston reduces braking on the left, so the right side does more of the work and the car pulls right.

Question 24: A rear disc brake system uses a small drum-in-hat parking brake assembly inside each rotor. After replacing the parking brake shoes, how is the adjustment typically made?

By tightening the parking brake cable until the lever is rigid
By pressing the brake pedal repeatedly until the shoes seat
By turning the star wheel adjuster through the access hole in the rotor until a slight drag is felt, then backing off (Correct answer)
By loosening the caliper bracket bolts and rotating the caliper

Correct answer: By turning the star wheel adjuster through the access hole in the rotor until a slight drag is felt, then backing off

The internal shoes are adjusted with a brake spoon at the star wheel, usually through an access hole in the hat of the rotor, until slight drag exists, then backed off per specification.

Question 25: A technician spins a wheel by hand with a digital multimeter on AC millivolts connected across a passive (variable-reluctance) wheel speed sensor. Which reading is expected from a good sensor?

A fixed resistance of 0 ohms that does not vary with wheel movement
An AC voltage that increases as the wheel is spun faster (Correct answer)
A square-wave signal with constant amplitude at every speed
A steady 5-volt DC signal that does not change with wheel speed

Correct answer: An AC voltage that increases as the wheel is spun faster

A variable-reluctance sensor generates its own AC signal from the changing magnetic field as the tone ring teeth pass. Both amplitude and frequency rise with wheel speed.

Question 26: Why should brake fluid from a container that has been left open for a long time not be used when refilling the reservoir?

It turns into a petroleum-based fluid
It becomes thicker and cannot enter the reservoir
It loses its dye, which makes leaks harder to find
It absorbs moisture, which lowers its boiling point and promotes corrosion (Correct answer)

Correct answer: It absorbs moisture, which lowers its boiling point and promotes corrosion

Glycol-based brake fluid is hygroscopic, so open containers take on moisture that lowers the boiling point and causes corrosion.

Question 27: A booster check valve is removed from a vacuum booster and tested with a hand-held vacuum pump. Which result indicates a good valve?

It holds vacuum in both directions
It passes air freely in both directions
It passes air only toward the booster side
It passes air only toward the engine side (Correct answer)

Correct answer: It passes air only toward the engine side

The check valve lets air be drawn out of the booster toward the intake manifold but blocks airflow back into the booster, which preserves the reserve vacuum.

Question 28: A technician uses a brake fluid tester and finds that the fluid's boiling point is well below the minimum for its DOT rating. What does this indicate?

The fluid has too high a viscosity for the system
The master cylinder has failed internally
The fluid has been contaminated with silicone and should be topped off
The fluid contains too much moisture and should be replaced (Correct answer)

Correct answer: The fluid contains too much moisture and should be replaced

Water absorbed by glycol-based fluid lowers the boiling point. A boiling-point reading below the rated minimum means the fluid should be replaced.

Question 29: What is the purpose of a residual pressure check valve in the master cylinder outlet for a drum brake circuit?

To limit pressure to the rear brakes during hard stops
To release trapped air to the atmosphere through the reservoir cap
To hold slight pressure in the line so the wheel cylinder cups stay sealed and air is kept from entering (Correct answer)
To prevent fluid from flowing back to the master cylinder when the pedal is applied

Correct answer: To hold slight pressure in the line so the wheel cylinder cups stay sealed and air is kept from entering

Residual check valves hold roughly 6–18 psi in drum brake lines, keeping the cup seals tight against the wheel cylinder bores and reducing air entry.

Question 30: When bench bleeding a master cylinder, why are the bleed tubes or fittings routed back into the reservoir with their ends below the fluid level?

To prevent air from being drawn back into the bore on the piston's return stroke (Correct answer)
To measure how far the piston travels
To raise fluid temperature during the procedure
To keep the piston seals lubricated with dry air

Correct answer: To prevent air from being drawn back into the bore on the piston's return stroke

Keeping the tube ends submerged means that only fluid, not air, is drawn back into the bore when the piston returns.

Question 31: A customer complains that the brake fluid level in the reservoir is slightly lower than at the last service. The vehicle has front disc brakes, and the pads are about half worn. A thorough inspection finds no leaks. What should the technician conclude?

The reservoir cap diaphragm has failed
The brake hoses are collapsing and need replacing
The master cylinder has failed internally and must be replaced
The level drop is normal because fluid fills the caliper pistons as the pads wear (Correct answer)

Correct answer: The level drop is normal because fluid fills the caliper pistons as the pads wear

As disc pads wear, the caliper pistons extend farther and take up fluid, so the reservoir level falls gradually.

Question 32: During a hydraulic test, the brake pedal slowly sinks toward the floor under steady foot pressure. No external leaks are found at the wheels, lines, or master cylinder, and the fluid level in the reservoir does not drop. What is the most likely cause?

Worn or leaking seals inside the master cylinder letting fluid bypass the piston (Correct answer)
A restricted brake hose collapsing internally
Excessive pushrod free play at the brake pedal
A stuck residual check valve

Correct answer: Worn or leaking seals inside the master cylinder letting fluid bypass the piston

A pedal that sinks slowly with no external leak and no loss of fluid points to internal bypass at the master cylinder piston seals.

Question 33: On a vehicle with traction control that shares the ABS hydraulic unit, what can the system do when a drive wheel starts to spin on a slippery surface?

Release the brakes on the non-spinning drive wheel to send it more torque
Lock the differential by applying all four brakes equally
Increase throttle opening to raise engine speed
Apply the brake at the spinning wheel and/or reduce engine torque (Correct answer)

Correct answer: Apply the brake at the spinning wheel and/or reduce engine torque

Traction control limits wheel spin by braking the spinning wheel and/or reducing engine output through throttle, spark or fuel control.

Question 34: A technician needs to replace the rear brake pads on a vehicle equipped with an electric parking brake motor mounted on each rear caliper. What is the correct way to retract the caliper piston?

Use a scan tool to put the system in service or maintenance mode (Correct answer)
Turn the piston in with a disc brake spreader tool
Open the bleeder and push the piston by hand
Compress the piston with a C-clamp

Correct answer: Use a scan tool to put the system in service or maintenance mode

The electric motor must retract the piston through its spindle drive using the scan tool's service mode, and forcing the piston back can damage the motor and gear mechanism.

Question 35: A vehicle has stability control codes and the warning light on after a wheel alignment that changed the steering wheel position. Which service is most likely required?

Replace both front wheel speed sensors
Calibrate or reset the steering angle sensor with a scan tool (Correct answer)
Replace the yaw rate sensor and the lateral accelerometer
Flush the brake fluid and replace the master cylinder

Correct answer: Calibrate or reset the steering angle sensor with a scan tool

The steering angle sensor zero point must match the straight-ahead position after an alignment or steering component service. A scan tool calibration relearns it.

Question 36: A technician installs a gauge in the front line and another in the rear line to test a combination valve's proportioning function. What should the gauges show when pedal pressure is well above the valve's split point?

Rear pressure higher than front pressure
Rear pressure equal to front pressure
Rear pressure rising more slowly than front pressure (Correct answer)
Rear pressure at zero

Correct answer: Rear pressure rising more slowly than front pressure

Above the split point, a working proportioning valve reduces the rate of rear pressure rise, so rear pressure falls progressively below front pressure.

Question 37: Why do many diesel-powered vehicles use an engine-driven or electric vacuum pump for the power brake booster?

Diesel engines produce too little intake manifold vacuum (Correct answer)
Diesel brake fluid requires higher pressure
Diesel vehicles cannot use hydraulic brakes
Diesel engines run too hot for a vacuum hose

Correct answer: Diesel engines produce too little intake manifold vacuum

Diesel engines are unthrottled, so they produce very little intake manifold vacuum, and a separate vacuum pump supplies the booster.

Question 38: A customer complains of a high-pitched squeal from the front brakes that occurs while driving and stops when the brake pedal is pressed lightly. What is the most likely cause?

Seized caliper slide pins
Cracked brake rotor
Air in the brake lines
Pad wear indicators contacting the rotors (Correct answer)

Correct answer: Pad wear indicators contacting the rotors

A wear indicator tab on the pad touches the rotor when the lining is nearly worn out. It makes a squeal that often stops when brake pressure is applied.

Question 39: All four wheels drag after the pedal is released. When the technician loosens the master cylinder outlet lines, the pressure releases and the wheels spin freely. Which is the most likely cause?

Seized caliper slide pins at all four wheels
Worn front brake pads
A leaking rear wheel cylinder
A plugged compensating port or a swollen cup in the master cylinder (Correct answer)

Correct answer: A plugged compensating port or a swollen cup in the master cylinder

If dragging stops when the lines are loosened at the master cylinder, pressure is being trapped upstream, so the master cylinder or its pushrod is at fault.

Question 40: After installing a new front brake hose, what check should be made before returning the vehicle to service?

Measure hose length against the old hose with the vehicle on a lift
Twist the hose one quarter turn to relieve stress on the fittings
Pressurize the hose to 5,000 psi with the engine off
Turn the steering wheel fully left and right and check for hose binding, stretching, or contact (Correct answer)

Correct answer: Turn the steering wheel fully left and right and check for hose binding, stretching, or contact

Steering and suspension movement must not stretch, kink or rub the hose. Turning lock to lock confirms there is enough slack and clearance.

Question 41: After driving, one front wheel is much hotter than the other and the vehicle pulls to that side when coasting. When the caliper bleeder is opened, the wheel spins freely. What is the most likely cause?

A collapsed inner lining in the brake hose (Correct answer)
A worn pad wear indicator
Excessive master cylinder reservoir fluid
A warped rotor on the opposite wheel

Correct answer: A collapsed inner lining in the brake hose

A damaged hose can act like a one-way valve. It lets fluid in under pedal pressure but doesn't let it return, so the pads keep clamping the rotor until the bleeder releases the trapped pressure.

Question 42: A brake pushrod gauge is used when installing a master cylinder on a power booster. What does the technician compare with this tool?

Brake pedal free play against pedal reserve distance
Booster pushrod protrusion against the depth of the master cylinder piston recess (Correct answer)
Reservoir fluid volume against the maximum fill line
Rotor thickness against the minimum specification

Correct answer: Booster pushrod protrusion against the depth of the master cylinder piston recess

The gauge checks that the booster pushrod length matches the master cylinder piston depth so the piston ends up with the correct clearance.

Question 43: Before adjusting a rear parking brake cable on a vehicle with rear drum brakes, what should the technician verify first?

The front brake pads are new
The parking brake lever is fully applied
The rear service brakes are in good condition and properly adjusted (Correct answer)
The brake fluid has been flushed

Correct answer: The rear service brakes are in good condition and properly adjusted

Parking brake cable adjustment compensates only for cable slack, so the shoes and self-adjusters must be in good order first to avoid a false adjustment.

Question 44: A vehicle with a hydro-boost system has a hard brake pedal and heavy steering, and a whining noise is heard from the engine compartment. Which is the most likely cause?

A slipping or broken power steering pump drive belt (Correct answer)
A leaking vacuum check valve
A worn parking brake cable
A faulty brake light switch

Correct answer: A slipping or broken power steering pump drive belt

Hydro-boost uses power steering pump pressure for assist, so a slipping or failed pump drive belt reduces both steering and brake assist.

Question 45: A rotor measures 0.980 in. thick. The discard thickness marked on the rotor is 1.000 in. What should the technician do?

Leave the rotor in place and replace only the pads
Resurface the rotor and install new pads
Replace the rotor (Correct answer)
Install shims behind the pads to make up the difference

Correct answer: Replace the rotor

The rotor is already below the discard thickness, so it no longer has enough mass to absorb heat or resist cracking. It must be replaced.

Question 46: Why must a brake fluid container be kept tightly capped when it is not in use?

Brake fluid evaporates quickly and the container would soon be empty
Exposure to light causes the fluid to become thicker and slower to flow
Air contact turns the fluid into a petroleum-like substance that swells seals
Glycol-based brake fluid absorbs moisture from the air, which lowers its boiling point (Correct answer)

Correct answer: Glycol-based brake fluid absorbs moisture from the air, which lowers its boiling point

DOT 3, 4 and 5.1 glycol-ether fluids are hygroscopic and absorb water. Absorbed water lowers the fluid's boiling point and promotes corrosion.

Question 47: Which is the main purpose of the metering valve in a front disc/rear drum brake system?

To delay front brake application until the rear shoes have overcome their return springs (Correct answer)
To turn on the dash warning lamp when one circuit loses pressure
To adjust rear pressure according to vehicle ride height
To limit rear brake pressure during hard stops

Correct answer: To delay front brake application until the rear shoes have overcome their return springs

The metering valve briefly holds off pressure to the front disc brakes so the rear drum shoes can begin to move. This gives more balanced application at low pedal pressure.

Question 48: When checking the air gap of an adjustable wheel speed sensor, which tool should the technician use?

A nonmagnetic (brass or plastic) feeler gauge or paper shim (Correct answer)
A dial indicator mounted on the brake rotor
A steel feeler gauge placed between the sensor and the tone ring
A micrometer measuring the sensor body diameter

Correct answer: A nonmagnetic (brass or plastic) feeler gauge or paper shim

A steel gauge would be attracted to the sensor magnet and give a false reading, so nonmagnetic feeler gauges or specified shims are used.

Question 49: A vehicle with a conventional dual-diagonal split hydraulic system is being bled, and the manufacturer gives no special sequence. Which wheel should be bled first?

The wheel farthest from the master cylinder (Correct answer)
The wheel closest to the master cylinder
Left front, because it is closest to the driver
Either rear wheel, then the fronts in any order

Correct answer: The wheel farthest from the master cylinder

Bleeding normally starts at the wheel with the longest line run from the master cylinder, which is usually the right rear. Air is then pushed out of the longest circuits first.

Question 50: After replacing an ABS hydraulic control unit (modulator), what is the recommended way to remove air trapped inside the unit?

Gravity bleed the unit by removing the cap and waiting 30 minutes
Pump the pedal with the ignition on until the ABS lamp turns off
Run the engine at high idle while opening all bleeders at once
Use a scan tool automated bleed procedure to cycle the valves and pump (Correct answer)

Correct answer: Use a scan tool automated bleed procedure to cycle the valves and pump

Air in the modulator valve body can only be expelled by commanding the solenoid valves and pump to operate, which a scan tool's bidirectional routine does.

Question 51: A customer complains of a hard brake pedal, and a hissing sound is heard from under the dash when the pedal is depressed. The engine also idles roughly when the brakes are applied. What is the most likely cause?

A restricted brake hose
A leaking booster diaphragm (Correct answer)
Worn rear brake shoes
A faulty brake light switch

Correct answer: A leaking booster diaphragm

A ruptured booster diaphragm lets air leak into the vacuum side, which causes the hiss, loss of assist, and a lean condition that makes the engine idle rough.

Question 52: When a Hall-effect (active) wheel speed sensor is viewed on a lab scope while the wheel turns faster, what change should be seen in the waveform?

A square wave of constant amplitude whose frequency increases (Correct answer)
A sine wave whose amplitude drops as speed rises
A flat line at battery voltage that never changes
The amplitude rises while the frequency stays the same

Correct answer: A square wave of constant amplitude whose frequency increases

Active sensors are powered by the ABS module and output a digital on/off signal. Speed is carried by frequency, not amplitude.

Question 53: A vehicle is brought in with an illuminated ABS light and traction control light after one tire was replaced with a significantly smaller-diameter tire. What is the most likely explanation?

The brake pedal switch is out of adjustment
The pump motor relay has failed open
The smaller tire rotates faster, so the module sees a wheel speed mismatch (Correct answer)
The brake fluid in the system has absorbed moisture

Correct answer: The smaller tire rotates faster, so the module sees a wheel speed mismatch

A smaller-diameter tire turns more revolutions per mile, so its wheel speed differs from the other wheels and the module may set a fault or disable the system.

Question 54: After the parking brake lever is released, the rear wheels still drag and the rear brakes overheat. Which is the most likely cause?

A seized or corroded parking brake cable (Correct answer)
An overfilled brake fluid reservoir
A leaking booster check valve
Low power steering fluid

Correct answer: A seized or corroded parking brake cable

A cable that is corroded or seized in its housing does not return fully, so the shoes or pads stay partly applied and the rear brakes drag.

Question 55: What causes the red brake warning lamp to light through a pressure differential switch?

Both circuits having equal pressure after a brake application
Fluid pressure rising above the proportioning valve split point
A drop in hydraulic pressure in one circuit shifts the valve piston into contact with the switch (Correct answer)
The metering valve opening fully at high line pressure

Correct answer: A drop in hydraulic pressure in one circuit shifts the valve piston into contact with the switch

If one circuit loses pressure, the higher pressure in the other circuit pushes the differential piston toward the low-pressure side. The piston closes the switch and lights the warning lamp.

ASE A5 Brakes Certification Test

The ASE A5 test certifies automotive technicians in diagnosing and repairing brake systems. It covers hydraulic, power assist and parking brakes, drum brakes, disc brakes, and electronic brake controls (ABS, traction and stability control).

Questions

75 min

Time Limit

70%

To Pass

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