ASE Automobile (A1–A8) — All Questions

A brake pedal that slowly sinks to the floor while held under steady pressure most likely indicates:

• a.Glazed brake pads
• b.A failing master cylinder (internal leak)✓
• c.Warped rotors
• d.Air in the lines only

A pedal that gradually falls under steady pressure indicates fluid bypassing internally in the master cylinder past worn seals. An external leak would lose fluid visibly. Replacing the master cylinder and bleeding the system restores a firm pedal.

Technician A says a spongy brake pedal is commonly caused by air in the hydraulic system. Technician B says air in the lines increases braking power. Who is correct?

• a.Neither A nor B
• b.Both A and B
• c.Technician B only
• d.Technician A only✓

Air is compressible, so it makes the pedal feel soft or spongy and reduces braking effectiveness; proper bleeding removes it. Technician B is wrong because air degrades rather than improves braking. Bleeding in the correct sequence restores a firm pedal.

Technician A says a pulsating brake pedal is usually caused by air in the hydraulic lines. Technician B says it is usually caused by rotor thickness variation or excessive lateral runout. Who is correct?

• a.Neither A nor B
• b.Technician A only
• c.Both A and B
• d.Technician B only✓

Thickness variation or warp causes the pads to move in and out as the disc turns, producing a pulsation felt in the pedal, while air produces a soft pedal instead. Technician B is correct. Measuring runout and thickness variation confirms it.

The primary purpose of a brake power booster is to:

• a.Store brake fluid
• b.Adjust the parking brake
• c.Prevent wheel lockup
• d.Reduce the pedal effort required to apply the brakes✓

The vacuum or hydraulic booster multiplies the driver's pedal force so less effort is needed for firm braking. A failed vacuum booster or leaking check valve produces a hard pedal. It works with, not instead of, the hydraulic system.

The main function of an anti-lock brake system (ABS) is to:

• a.Eliminate the need for brake pads
• b.Replace the parking brake
• c.Prevent wheel lockup and maintain steering control during hard braking✓
• d.Increase brake fluid pressure permanently

ABS pulses hydraulic pressure to keep wheels from locking so the driver retains steering control and shortens stopping distance on most surfaces. Wheel-speed sensors feed the control module, which modulates the hydraulic unit. A fault typically turns on the ABS warning lamp and disables the function.

A wheel-speed sensor signal that is missing on one wheel will most likely cause the ABS to:

• a.Lock all four wheels
• b.Increase engine power
• c.Set a code and disable ABS, reverting to normal braking✓
• d.Apply the parking brake

A lost wheel-speed signal sets a DTC and usually disables ABS, leaving conventional (non-anti-lock) braking available. The ABS warning lamp illuminates. Common causes include a damaged sensor, wiring, or a contaminated tone ring.

Brake fluid is hygroscopic, which means it:

• a.Repels all water
• b.Absorbs moisture from the air over time✓
• c.Expands when frozen
• d.Conducts electricity

Glycol-based brake fluid absorbs moisture, which lowers its boiling point and can cause corrosion and a spongy pedal from vapor under heavy braking. This is why periodic fluid replacement is recommended. Sealed containers and prompt cap replacement limit moisture uptake.

During a disc brake job, a technician should measure rotor thickness and compare it to the:

• a.Toe specification
• b.Tire pressure specification
• c.Minimum (discard) thickness stamped on the rotor✓
• d.Battery voltage

Rotors must remain above the minimum thickness (often cast or stamped on the rotor) to dissipate heat and resist warping. A rotor below spec must be replaced, not machined. Measuring with a micrometer at several points also reveals thickness variation.

Technician A says brake shoes are used in disc brakes. Technician B says brake shoes are used in drum brakes. Who is correct?

• a.Neither A nor B
• b.Both A and B
• c.Technician B only✓
• d.Technician A only

Drum brakes use curved shoes that press outward against the drum, while disc brakes use flat pads that clamp a rotor. Technician B is correct. Many vehicles combine front discs with rear drums or discs.

Technician A says a grinding, metal-on-metal noise during braking indicates friction material worn past its limit. Technician B says continued driving in that condition can score the rotor or drum. Who is correct?

• a.Technician B only
• b.Neither A nor B
• c.Technician A only
• d.Both A and B✓

When friction material wears away, the metal backing contacts the rotor or drum, producing a grinding noise, and continued driving scores the surface and raises repair cost. Both technicians are correct. Immediate pad or shoe replacement and surface inspection are required.

A rear disc parking brake that will not hold is often caused by:

• a.A misadjusted or seized parking brake mechanism/cable✓
• b.Air in the front lines
• c.Low battery voltage
• d.A failed wheel-speed sensor

Parking brake holding faults usually trace to cable stretch, misadjustment, or a seized caliper parking mechanism. Proper adjustment and lubrication restore holding force. On integral rear calipers, the internal actuator must function for both service and parking braking.

A brake caliper that sticks and does not release will most likely cause:

• a.A hard pedal at all times
• b.Dragging, overheating, and pulling to that side✓
• c.A soft pedal only
• d.Loss of all braking

A seized caliper keeps the pads applied, causing drag, excessive heat, uneven pad wear, and a pull toward that wheel. Overheated fluid can boil and reduce braking. Rebuilding or replacing the caliper and inspecting the slides and hose corrects it.

The metering valve in a combination valve is used to:

• a.Warn of ABS faults
• b.Bleed the master cylinder
• c.Increase rear brake pressure
• d.Delay front disc application so rear drums engage together✓

The metering valve holds off front disc pressure briefly so the rear drum shoes overcome their return springs and apply at nearly the same time, balancing braking. The proportioning section limits rear pressure to prevent lockup. Together these balance front-to-rear braking.

When bleeding a conventional hydraulic brake system, the general rule is to bleed:

• a.Only the front wheels
• b.All wheels at the same time
• c.In the sequence specified by the manufacturer, often longest line first✓
• d.Starting at the wheel nearest the master cylinder

Manufacturers specify a bleeding sequence, frequently starting at the wheel farthest from the master cylinder, to purge air effectively. Following the correct order and keeping the reservoir full prevents introducing more air. Some ABS units require a scan tool to bleed fully.

A proportioning valve in the brake system is designed to:

• a.Store extra brake fluid
• b.Reduce pressure to the rear brakes to prevent early lockup✓
• c.Increase pressure to the front only
• d.Operate the parking brake

Because weight shifts forward during braking, the proportioning valve limits rear brake pressure to keep the rear wheels from locking prematurely. This maintains stability during hard stops. Many vehicles now handle this function electronically through ABS/EBD.

Technician A says silicone (DOT 5) and glycol (DOT 3/4) brake fluids can be freely mixed. Technician B says brake fluid type is unimportant. Who is correct?

• a.Technician B only
• b.Both A and B
• c.Technician A only
• d.Neither A nor B✓

Silicone and glycol fluids are not compatible and must not be mixed, and using the wrong fluid type can damage seals and reduce performance. Both technicians are incorrect. Always use the fluid specification listed for the vehicle.

The hydraulic brake system transmits force to all wheels based on the principle that:

• a.Liquids expand in volume when they are put under high pressure
• b.Fluid pressure gradually decreases as it travels farther from the pedal
• c.Pressure on a confined fluid is transmitted equally throughout✓
• d.Fluid compresses under pressure and stores energy to release later

Pascal's principle states that pressure in a confined, incompressible fluid is transmitted undiminished throughout, which is why pedal force reaches every wheel. Air in the system defeats this because air compresses. This is the basis of hydraulic braking.

A modern tandem (dual) master cylinder is designed so that:

• a.Both hydraulic circuits fail together the moment one springs a leak
• b.A leak in one circuit still leaves the other working✓
• c.It boosts pedal effort by itself without any vacuum or hydraulic assist
• d.It also stores and supplies fluid for the vehicle's clutch system

The tandem master cylinder splits braking into two independent hydraulic circuits so that a single leak leaves partial braking rather than total loss. The pedal travels farther and the warning light comes on. This redundancy is a required safety feature.

The red brake warning light (not the ABS lamp) can be triggered by:

• a.Low fluid or a pressure difference between the two circuits✓
• b.A dirty cabin air filter that has restricted airflow from the vents
• c.A high engine coolant temperature approaching the overheat point
• d.A worn wheel-speed sensor sending an erratic signal to the module

The base brake warning lamp responds to low reservoir fluid, an applied parking brake, or a pressure imbalance sensed by the differential switch. It signals a hydraulic problem needing attention. The separate amber ABS lamp covers anti-lock faults.

Drum brakes use a self-adjuster mechanism that typically operates when the:

• a.Vehicle is parked and left on a steep hill with the brake applied
• b.Wheels are removed from the vehicle during a routine tire rotation
• c.Ignition switch is first turned on before the engine begins to crank
• d.Brakes are applied while the vehicle is backing up✓

Many drum self-adjusters take up shoe clearance during reverse stops, turning the star wheel a little at a time. If the mechanism seizes, the pedal gets low as the shoes wear. Proper adjustment restores a high, firm pedal.

A wheel cylinder leaking brake fluid onto the drum brake shoes will cause:

• a.An increase in fuel economy from lower rolling resistance at that wheel
• b.An overcharged battery from the extra draw on the charging system
• c.Contaminated linings and reduced or grabby braking there✓
• d.A high, firm pedal that requires very little effort to fully stop

A leaking wheel cylinder soaks the shoes with fluid, ruining the friction material and causing grab or reduced braking. Both the cylinder and shoes must be replaced. Fluid on the drum also signals the leak.

Brake fade after repeated hard stops, where the pedal stays firm but braking weakens, is most often:

• a.A cracked windshield distracting the driver during the hard stops
• b.Mechanical fade from overheated linings losing friction✓
• c.A worn front wheel bearing that has developed play and roughness
• d.Air being drawn into the master cylinder past its worn primary seal

When linings overheat they temporarily lose their friction coefficient, so the pedal feels normal but stopping power drops. Fluid fade, by contrast, gives a soft pedal from boiling fluid. Cooling and quality linings reduce mechanical fade.

After machining a brake rotor on a lathe, the technician should apply a:

• a.Bead of RTV silicone around the rotor edge to reduce vibration
• b.Non-directional finish and clean it before installing pads✓
• c.Layer of thread sealant to the rotor hat where it meets the hub
• d.Thin coat of high-temperature grease across the rotor friction surface

A non-directional finish helps the new pads seat and prevents pad noise or pull, and the surface is cleaned of metal dust before assembly. Directional swirl marks can act like a screw thread. Proper prep improves braking and reduces comebacks.

Excessive lateral runout of a brake rotor is measured with a:

• a.Test light probed across the wheel-speed sensor connector
• b.Vacuum gauge connected to a port on the power brake booster
• c.Feeler gauge inserted between the brake pad and the rotor surface
• d.Dial indicator reading against the rotor face✓

A dial indicator mounted to read the spinning rotor face shows lateral runout, which over time creates thickness variation and pedal pulsation. Excess runout may come from the rotor, hub, or debris behind the rotor. It is corrected by machining, indexing, or replacement.

A seized caliper slide pin will most likely cause:

• a.Uneven (tapered) pad wear and a possible pull✓
• b.An evaporative emission leak code from the fuel vapor canister
• c.A charging system fault that lights the battery warning lamp
• d.A boiling radiator and rapid loss of coolant from the overflow

When a slide pin sticks, the caliper cannot center over the rotor, so one pad wears faster and the vehicle may pull. Cleaning, lubricating, or replacing the pins and boots restores even movement. Neglected pins also cause drag and heat.

Compared with semi-metallic pads, ceramic brake pads are generally chosen for:

• a.Lower noise and less visible brake dust✓
• b.Higher rotor wear under every driving condition and temperature
• c.A lower purchase cost being their single and only real advantage
• d.The greatest possible heat capacity for sustained racing use only

Ceramic pads typically run quieter and produce lighter-colored, less-visible dust, which suits many passenger vehicles. Semi-metallic pads handle high heat well but can be noisier and dustier. Pad choice balances noise, dust, and heat needs.

A constant high-pitched squeal that stops when the brakes are applied usually indicates:

• a.The pad wear indicator dragging on the rotor✓
• b.Air trapped in the master cylinder past the worn primary piston seal
• c.A worn front wheel bearing that drones and changes with vehicle speed
• d.A leaking wheel cylinder soaking the rear drum brake shoes with fluid

The mechanical wear indicator drags on the rotor when the pads are thin, squealing until the brakes are pressed. It is a warning to replace the pads soon. Ignoring it leads to metal-to-metal grinding and rotor damage.

The check valve in a vacuum brake booster is designed to:

• a.Bleed atmospheric air into the booster to firm up the brake pedal
• b.Adjust the parking brake cable tension automatically as pads wear
• c.Hold vacuum in the booster so a reserve is available✓
• d.Regulate hydraulic brake fluid pressure sent out to the four calipers

The one-way check valve traps engine vacuum in the booster so the driver gets assisted stops even after the engine stops or during low-vacuum conditions. A faulty valve gives a hard pedal or loss of reserve. It is a simple but important part.

A hydro-boost power brake system gets its assist from:

• a.The power steering pump's hydraulic pressure✓
• b.Exhaust backpressure captured and stored to help apply the brakes
• c.The alternator's electrical output routed to a motor on the booster
• d.Engine intake manifold vacuum, the same source used by a diaphragm booster

Hydro-boost uses pressurized power steering fluid instead of vacuum to provide brake assist, common on diesels and heavy vehicles with little manifold vacuum. A steering or belt problem can affect braking assist. It stores a small hydraulic reserve for stops after shutdown.

The ABS hydraulic control unit prevents lockup by:

• a.Applying the parking brake automatically during a hard braking event
• b.Adding engine intake vacuum to each individual wheel brake circuit
• c.Increasing the master cylinder bore size to raise hydraulic pressure
• d.Cycling solenoid valves to modulate pressure at a wheel✓

The modulator's solenoid valves cycle to hold, release, and reapply pressure at a wheel that is about to lock, based on wheel-speed data. This keeps the wheels rolling for steering control. The pump restores pressure during release cycles.

A damaged or contaminated tone ring (reluctor) at one wheel will most likely cause:

• a.A parking brake that will not hold the vehicle on a moderate grade
• b.A boiling master cylinder that overflows the brake fluid reservoir
• c.An erratic wheel-speed signal and false ABS activation or a code✓
• d.A soft, spongy brake pedal from air trapped in the hydraulic system

A cracked, rusty, or debris-covered tone ring produces an irregular signal, which the ABS module may read as a wheel about to lock, causing false activation or a code. Inspecting and cleaning or replacing the ring corrects it. The sensor air gap is also checked.

Electronic stability control (ESC) and traction control generally operate by using:

• a.The air conditioning compressor to add drag at the wheel that is slipping
• b.The evaporator core temperature sensor to detect a loss of traction
• c.The ABS wheel-speed sensors and hydraulic modulator✓
• d.The alternator diodes to divert electrical load away from the drive wheels

ESC and traction control build on ABS hardware, using wheel-speed and yaw data to apply individual brakes and cut engine torque to keep the vehicle stable. A shared sensor fault can disable all three systems. They enhance, not replace, the base brakes.

Steel brake lines are joined and sealed using a:

• a.Soldered lap joint that bonds the two line ends permanently together
• b.Double flare or ISO flare rated for high pressure✓
• c.Simple compression sleeve and nut like those used on water supply lines
• d.Rubber grommet pushed into the fitting to seal against fluid leakage

Brake lines must use a double (or ISO) flare designed to hold high hydraulic pressure safely; ordinary compression fittings are not approved for brake lines. A single flare can crack and leak. The correct flare and fittings ensure a reliable seal.

Before installing a new or rebuilt master cylinder, the technician should:

• a.Pack the internal bore and pistons with wheel bearing grease first
• b.Place it in a freezer overnight to shrink the seals for installation
• c.Fill the reservoir with power steering fluid and cycle the pistons
• d.Bench bleed it to remove the trapped air✓

Bench bleeding purges air from the master cylinder on the bench so the brakes can be bled properly after installation. Skipping this step traps air and gives a low, spongy pedal. Only the specified brake fluid is used.

A deteriorated flexible brake hose with an internal flap can act like a one-way valve, causing:

• a.One brake to drag because pressure cannot fully release✓
• b.An evaporative emission leak code from the fuel vapor canister
• c.Both rear brakes to lock together during any moderate stop
• d.A charging system fault that illuminates the battery warning lamp

When a hose breaks down internally, a flap can let pressure through but block its return, so that caliper stays partly applied and drags. The wheel overheats and pulls. Replacing the hose restores normal release.

A pulsation felt in the brake pedal that occurs mainly with rear drum brakes is most often caused by:

• a.Air trapped in the master cylinder past its worn primary piston seal
• b.An out-of-round brake drum✓
• c.A dirty cabin air filter restricting airflow through the HVAC case
• d.A worn oxygen sensor that has slowed its response in the exhaust

An out-of-round drum changes the shoe-to-drum contact as it rotates, producing a pulsation. Measuring the drum diameter at several points reveals it. Machining within limits or replacing the drum corrects it.

When bleeding brakes, keeping the master cylinder reservoir topped off matters because:

• a.Running it dry lets air back into the system✓
• b.It keeps the battery charged during the bleeding procedure
• c.It automatically adjusts the parking brake cable as fluid is added
• d.It cools the engine by circulating brake fluid through the radiator

If the reservoir empties during bleeding, the master cylinder draws in air and you have to start over. Maintaining the level keeps the process moving forward. Using fresh, correct-spec fluid also matters.

Approved caliper grease is applied to the caliper slide pins to:

• a.Let the caliper move freely and prevent binding✓
• b.Seal the hydraulic circuit against leaks at the caliper piston bore
• c.Provide extra friction between the brake pad and the rotor surface
• d.Raise the brake fluid's boiling point during hard repeated braking

Proper lubricant on the slide pins lets the caliper float and clamp evenly, preventing drag and uneven pad wear. The grease must be compatible with the rubber boots. Never put lubricant on the friction surfaces.

A vehicle pulls to one side during braking. All of the following can cause this EXCEPT:

• a.A restricted brake hose on one side limiting release at that wheel
• b.Contaminated linings on one wheel that grab or slip unevenly
• c.A seized caliper on one side that keeps its pads partly applied
• d.A pad set worn evenly the same amount on both front wheels✓

A brake pull comes from unequal braking side to side, such as a seized caliper, a restricted hose, or contaminated linings; pads worn evenly on both sides brake equally and do not pull. Diagnosis compares the two sides. Correcting the uneven condition centers the braking.

Brake linings that have become glazed (hard and shiny) from overheating will typically cause:

• a.A slow coolant leak from the engine's cooling system passages
• b.Reduced braking and noise until the linings are renewed✓
• c.A spongy, low pedal caused by air in the hydraulic brake lines
• d.An overcharged battery from extra load on the charging system

Glazing hardens the friction surface so it grips less and may squeal, lowering braking performance. Light glazing can sometimes be sanded, but badly glazed linings are replaced. Correcting the cause of overheating, such as a dragging caliper, prevents recurrence.

When the ABS warning lamp is on but the red brake lamp is off, the vehicle usually has:

• a.A parking brake that has locked and will not release the rear wheels
• b.No braking capability at all until the fault has been fully repaired
• c.A boiling master cylinder overflowing fluid from the reservoir cap
• d.Normal base braking with anti-lock disabled✓

An ABS-only fault disables anti-lock control but leaves conventional hydraulic braking working, so the pedal still stops the vehicle. The red lamp would indicate a base hydraulic problem instead. The ABS fault is diagnosed with a scan tool.

A banjo bolt connecting a brake hose to a caliper should be reassembled with:

• a.No sealing washers at all as long as the bolt is tightened firmly
• b.New copper crush washers, torqued to spec✓
• c.A coat of anti-seize applied to both of the washer sealing faces
• d.The original washers reused along with thread sealant on the bolt

Banjo fittings seal with soft copper crush washers that deform once, so new washers and proper torque are needed to prevent a leak. Reused washers often weep fluid. The banjo bolt has hollow passages for fluid flow.

The dry boiling point of a brake fluid is higher than its wet boiling point because:

• a.Absorbed moisture over time lowers the boiling point✓
• b.Pressure inside the sealed brake system has no effect on boiling
• c.The fluid gains fresh additives and improves as it ages in service
• d.Cold outdoor weather raises the fluid's boiling point substantially

Glycol brake fluid absorbs moisture in service, and that water lowers the boiling point, which is why the wet rating is lower than the fresh dry rating. Boiled fluid produces vapor and a spongy pedal. Periodic fluid replacement restores the margin.

Brake rotor thickness variation (parallelism) differs from lateral runout in that thickness variation is measured with a:

• a.Vacuum gauge connected to a port on the vacuum brake booster
• b.Micrometer at several points around the rotor✓
• c.Feeler gauge slipped between the brake pad and rotor at each wheel
• d.Dial indicator reading against the flat face of the spinning rotor

Thickness variation is the difference in rotor thickness measured with a micrometer at points around the disc, while runout is side-to-side wobble read with a dial indicator. Both cause pedal pulsation but are checked differently. Excess of either is corrected by machining or replacement.

A low brake pedal after a drum brake service, with no leaks or air, most often means the:

• a.Shoes need adjustment to reduce excess clearance✓
• b.Rotors have been machined thicker than the original specification
• c.Booster vacuum supply is much higher than the engine can produce
• d.Master cylinder bore is far too large for the vehicle's brake system

Freshly installed shoes with too much clearance require several pedal strokes or manual adjustment to take up, causing a low pedal until adjusted. The self-adjusters or a manual adjustment set the clearance. A properly adjusted drum brake gives a high pedal.

A firm pedal that requires very high effort, with the engine running, most likely indicates a problem with the:

• a.Parking brake cable that has stretched and gone out of adjustment
• b.Wheel-speed sensor sending an erratic signal to the ABS control module
• c.Vacuum booster or its vacuum supply✓
• d.ABS tone ring that has cracked or become coated with road debris

A failed booster, leaking check valve, or lost vacuum supply removes the assist, leaving a hard, high-effort pedal even though the hydraulics are fine. Checking vacuum at the booster and the check valve isolates it. The brakes still work but require much more force.

The residual pressure (check) valve sometimes used in drum brake circuits is designed to:

• a.Raise rear brake pressure only during an anti-lock braking event
• b.Store extra brake fluid to also supply the hydraulic clutch system
• c.Block the parking brake from applying while the vehicle is moving
• d.Keep slight line pressure so wheel cylinder cups stay seated✓

A small residual pressure keeps the wheel cylinder cup lips seated so air is not drawn in and response stays quick. It is used on drum circuits, not on disc circuits, which need full release. The proportioning or metering functions are separate.

Grease or brake fluid contamination on one set of brake linings typically causes:

• a.A charging system fault that turns on the battery warning lamp
• b.A pull or grab toward that wheel✓
• c.A perfectly balanced, straight stop with no change in braking feel
• d.A slow coolant leak from the engine's cooling system passages

Contaminated friction material changes that wheel's braking, causing the vehicle to grab or pull to one side. The source of contamination, such as a leaking seal or caliper, must be fixed and the linings replaced. Cleaning alone rarely restores the friction material.

During pressure or gravity brake bleeding, the goal is to:

• a.Purge air from the lines so the pedal is firm✓
• b.Adjust the wheel bearing preload at each corner of the vehicle
• c.Raise the boiling point of the brake fluid already in the system
• d.Add a small amount of air to soften the pedal for easier modulation

All bleeding methods remove compressible air so the pedal becomes firm and braking is consistent. Pressure, vacuum, gravity, and manual methods all achieve this. Some ABS units require a scan tool to cycle the modulator during bleeding.

Technician A says a seized caliper can cause a pull and a burning smell from overheating. Technician B says it can boil the brake fluid and cause a fade. Who is correct?

• a.Neither A nor B
• b.Technician A only
• c.Technician B only
• d.Both A and B✓

A stuck caliper drags, overheating that wheel, which causes a pull, odor, and can boil the fluid into vapor. Both technicians are correct. The caliper, slides, and hose are inspected to find the cause.

Technician A says ignored worn brake pads can score the rotor. Technician B says continued metal-to-metal braking reduces stopping power. Who is correct?

• a.Technician B only
• b.Neither A nor B
• c.Both A and B✓
• d.Technician A only

When the friction material is gone, the metal backing grooves the rotor and braking suffers. Both technicians are correct. Timely pad replacement avoids rotor damage and a longer stop.