Ten ASE A5 Brakes questions in the ASE format: four options, one best answer. They are free to use, print and share, and there is nothing to sign up for on this page.
01How to use these
The questions come from the ToolboxPrep A5 bank and are spread across the test's content areas in the proportion the ASE test specification gives them: A (Hydraulic, Power Assist, and Parking Brake Systems Diagnosis and Repair), B (Drum Brake Diagnosis and Repair), C (Disc Brake Diagnosis and Repair), D (Electronic Brake Control Systems: Antilock Brake System (ABS), Traction Control System (TCS), and Electronic Stability Control System (ESC) Diagnosis and Repair). Answer each one before opening the explanation. Every explanation covers all four options, because knowing why the wrong answers are wrong is most of the skill.
- Pace. The A5 test gives you 75 minutes for 55 questions (45 scored, 10 unscored), about 1 min 22 s a question. Try these at that pace.
- Print. The printed version shows the questions and the answer key without the explanations, so it works as a handout.
02The questions
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What is the job of the compensating (vent) port in a master cylinder bore?
- It holds light residual pressure in the lines after the pedal is released.
- It feeds fluid behind the piston cup so a fast release does not draw in air.
- It opens the pressure chamber to the reservoir when the pedal is released.
- It balances pressure between the two circuits during a hard stop.
Show the answer
C. Correct. With the pedal released, the cup sits just behind the compensating port, so fluid can move between the bore and the reservoir as it expands with heat or returns from the wheels. Once the cup moves past the port the chamber is sealed and pressure builds; a covered port traps pressure and makes the brakes drag.
Why not the others
A. Holding residual pressure is the job of a residual check valve, used at the outlet of some drum brake circuits. The compensating port does the opposite: it lets the chamber return to reservoir pressure at rest.
B. Feeding fluid to the area behind the cup is the job of the larger inlet (replenishing) port. The compensating port is the small port ahead of the cup that vents the pressure chamber to the reservoir at rest.
D. The compensating port plays no part in the pressure either circuit builds during a stop; once the cups pass the ports, the floating secondary piston is what lets the two chambers build nearly equal pressure. The compensating port vents each pressure chamber to the reservoir with the pedal released.
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Which wrench should be used on the brake line tube nuts when removing and installing a master cylinder?
- An adjustable wrench
- An open-end wrench
- A flare-nut wrench
- A pair of locking pliers
Show the answer
C. Correct. A flare-nut (line) wrench grips more of the soft tube nut's flats than an open-end wrench but has an opening that passes over the line, so it turns the nut without spreading or rounding it. Where a torque is specified, a flare-nut crowfoot on a torque wrench is used.
Why not the others
A. An adjustable wrench grips only two flats and its jaw can shift, so it rounds tube nuts even more readily than an open-end wrench. A flare-nut wrench is the tool for brake tube nuts.
B. An open-end wrench grips only two flats and spreads under load, which easily rounds a soft, often corroded tube nut. A flare-nut wrench grips more of the nut while still passing over the line.
D. Locking pliers crush and chew the flats of a tube nut and can collapse the tubing behind it. Tube nuts are turned with a flare-nut wrench, which grips the flats without damaging them.
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What does a pressure differential valve do when one of the two hydraulic circuits loses pressure?
- Its piston moves to the failed side and closes the lamp switch.
- It shuts off fluid flow to the failed circuit to save the fluid.
- It routes fluid from the working circuit to the failed circuit.
- It lowers pressure in the working circuit to keep braking balanced.
Show the answer
A. Correct. The valve's piston is held centered by equal pressure from both circuits; when one side loses pressure, the other side pushes the piston toward the failed side, and it operates the switch that turns on the brake warning lamp. It warns the driver but does not change how either circuit brakes.
Why not the others
B. The pressure differential valve does not close off a circuit; a leak keeps leaking each time the pedal is applied. Its piston only shifts to switch on the warning lamp.
C. The two circuits are kept separate so a leak in one cannot drain the other; the valve never passes fluid between them. Its piston shifts toward the failed side and switches on the warning lamp.
D. Nothing lowers the working circuit's pressure; the driver simply has half the system and a longer stop. The valve's job is to switch on the warning lamp.
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Before measuring brake pedal free travel on a vehicle with a vacuum booster, the manufacturer's procedure has the technician pump the pedal several times with the engine off. What is the purpose of this step?
- To seat the booster check valve against manifold vacuum
- To push any air out of the master cylinder before measuring
- To recenter the pressure differential valve before measuring
- To exhaust the booster's stored vacuum before measuring
Show the answer
D. Correct. Vacuum stored in the booster lets its control valve begin assisting as the pedal moves, which can change how much free travel is felt. Exhausting the reserve first means the measurement shows only the mechanical clearance in the pedal, pushrod and valve linkage, which is then compared with the manufacturer's specification.
Why not the others
A. With the engine off there is no manifold vacuum to seat the check valve against, and the valve does not set free travel. Pumping the pedal empties the booster's stored vacuum before the measurement.
B. Pumping the pedal with the bleeders closed does not remove air from the master cylinder. The step uses up the booster's stored vacuum so it does not affect the free-travel reading.
C. The pressure differential valve does not affect pedal free travel, and pumping the pedal is not how it is centered. The step exhausts the booster's vacuum reserve so only linkage clearance is measured.
-
A vehicle pulls during braking. Fluid runs out when the right rear wheel cylinder boot is lifted, and the right rear linings are soaked with brake fluid. The left rear brake is dry and its linings are within specification. Which repair is correct?
- Replace the right wheel cylinder and right rear shoes only
- Replace the right wheel cylinder and clean the right linings
- Replace the right wheel cylinder and both rear shoe sets
- Replace both rear shoe sets and bleed the system
Show the answer
C. Correct. The leaking cylinder must be replaced, and friction material soaked with brake fluid cannot be cleaned back to its original friction. Shoes are replaced in axle sets so both rear brakes grip alike; clean the drum and backing plate, then bleed the system.
Why not the others
A. New linings on one side and worn ones on the other grip differently and can still pull. Shoes are replaced in axle sets, so both rear shoe sets are replaced along with the leaking right cylinder.
B. Brake cleaner removes fluid from the surface but not from inside the lining, which has absorbed it and no longer grips like the other side. The soaked shoes are replaced, along with the left rear shoes as an axle set.
D. New shoes alone would soon be soaked again because the right wheel cylinder is still leaking past its cups. The cylinder is replaced along with both rear shoe sets.
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A vehicle pulls to the right only when the brakes are applied. Tire pressures and sizes match, the vehicle tracks straight while cruising, and both front calipers release fully and slide freely on their pins. Which of these could be the cause?
- Grease-soaked pads at the right front
- Grease-soaked pads at the left front
- Excessive lateral runout of the left rotor
- A vacuum brake booster with weak assist
Show the answer
B. Correct. Grease on the left pads lowers their friction, so the right brake does more of the work and the vehicle pulls right. Soaked pads cannot be cleaned; the grease leak is repaired and the pads are replaced on both sides of the axle.
Why not the others
A. Grease on the right pads would weaken the right brake, and the vehicle would pull left, toward the stronger left brake.
C. Lateral runout makes the rotor wobble, knocking the pads back and wearing in thickness variation that is felt as pulsation; it does not produce a steady pull to one side.
D. A weak booster raises pedal effort for both front brakes equally, so it lengthens stops without pulling the vehicle to either side.
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An outside micrometer reads a front rotor at eight points around it, the same distance from the edge: 1.104, 1.103, 1.105, 1.102, 1.104, 1.103, 1.104 and 1.103 in. The manufacturer's limits are 0.0005 in. maximum thickness variation, 1.039 in. machine-to and 1.024 in. discard. What should be done?
- Index the rotor and measure again
- Return the rotor to service as it is
- Replace the rotor with a new one
- Machine the rotor and recheck it
Show the answer
D. Correct. Thickness variation is the largest reading minus the smallest: 1.105 - 1.102 = 0.003 in., six times the 0.0005 in. limit. The thinnest point is 0.063 in. above the 1.039 in. machine-to dimension, so a cleanup cut can remove the variation and leave the rotor in limits.
Why not the others
A. Indexing changes how hub and rotor runout stack up; thickness variation is in the rotor itself and moves with it, so indexing cannot reduce it.
B. The thinnest reading, 1.102 in., is well above the 1.039 in. machine-to dimension, but the variation is 1.105 - 1.102 = 0.003 in., six times the 0.0005 in. limit, so the rotor cannot go back as it is.
C. Replacement is for a rotor that cannot be brought into limits; here the thinnest point is 0.063 in. above the machine-to dimension, far more than the cleanup cut needed to remove a 0.003 in. variation.
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Why does a disc brake need more hydraulic pressure than a duo-servo drum brake to produce the same stopping force?
- Caliper pistons are smaller than wheel cylinder pistons
- The pads get no self-energizing help from the rotor
- The square-cut seal absorbs much of the pressure
- Pad linings have far less friction than shoe linings
Show the answer
B. Correct. In a duo-servo drum the turning drum drags the shoes into it and the primary shoe helps apply the secondary, multiplying the force; a caliper's clamping force comes only from hydraulic pressure on its pistons. Disc systems make up for it with large pistons and power assist.
Why not the others
A. Caliper pistons are larger than wheel cylinder pistons, which raises clamping force; the extra pressure is needed because the pads get no self-energizing help.
C. The seal flexes only slightly and takes almost none of the pressure; the difference is that the drum's rotation helps apply the shoes while the rotor gives the pads no such help.
D. Pad and shoe linings work in a similar friction range; the difference is the drum's self-energizing action, which a caliper does not have.
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The service information for a hybrid sedan with an electronically controlled (brake-by-wire) brake system says to disable the system with the scan tool's service mode before replacing the front pads. The reason is that, outside service mode, the system:
- will erase the stored wheel speed sensor calibration if a caliper is unbolted.
- can recharge the high-voltage battery through the front wheels by hand.
- can pressurize the brake hydraulics even with the vehicle switched off.
- will lock the front wheels with the parking brake and keep them from turning.
Show the answer
C. Correct. These systems use a pump and accumulator under module control, and a pressed pedal or an opened door can wake them and build pressure with the power switch off. Disabling the system first keeps a caliper from clamping on a hand or pushing a piston out while the pads are out.
Why not the others
A. Unbolting a caliper has no effect on wheel speed sensor data, which comes from the sensor and its tone ring or encoder. The hazard being prevented is the brake system pressurizing itself while a caliper is apart.
B. Turning a wheel by hand on a lift is not what service mode guards against. Service mode keeps the brake pump and accumulator from pressurizing the calipers while the pads are out.
D. On a typical hybrid sedan the parking brake acts on the rear wheels, and it is not what makes front pad work hazardous. The concern is the electronically controlled pump and accumulator applying hydraulic pressure on their own.
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The service information for an ESC vehicle calls for the scan-tool automated bleed only when air may have entered the hydraulic control unit; otherwise a base-brake bleed at the wheels is enough. Which of these jobs calls for the automated bleed?
- Replacing a front brake hose between the line and caliper
- Refilling a master cylinder reservoir that was found empty
- Replacing a rear caliper with its brake hose clamped off
- Replacing front pads after pushing the caliper pistons back
Show the answer
B. Correct. An empty reservoir lets the master cylinder draw air, and pedal strokes push it into the lines that feed the hydraulic control unit. Because air may now be inside the unit, the stated rule calls for the automated bleed.
Why not the others
A. The hose is downstream of the hydraulic unit, so air enters only the line to that caliper. A base-brake bleed at that wheel removes it under the stated rule.
C. Air enters only at the new caliper, past the hydraulic unit. A base-brake bleed at that wheel is the stated procedure.
D. Pushing the pistons back moves fluid but lets no air into the system, so the stated rule does not call for the automated bleed. The fluid level is checked after the pedal is pumped up.
03Answer key
| Question | Answer | Content area |
|---|---|---|
| Q1 | C | Hydraulic, Power Assist, and Parking Brake Systems Diagnosis and Repair |
| Q2 | C | Hydraulic, Power Assist, and Parking Brake Systems Diagnosis and Repair |
| Q3 | A | Hydraulic, Power Assist, and Parking Brake Systems Diagnosis and Repair |
| Q4 | D | Hydraulic, Power Assist, and Parking Brake Systems Diagnosis and Repair |
| Q5 | C | Drum Brake Diagnosis and Repair |
| Q6 | B | Disc Brake Diagnosis and Repair |
| Q7 | D | Disc Brake Diagnosis and Repair |
| Q8 | B | Disc Brake Diagnosis and Repair |
| Q9 | C | Electronic Brake Control Systems: Antilock Brake System (ABS), Traction Control System (TCS), and Electronic Stability Control System (ESC) Diagnosis and Repair |
| Q10 | B | Electronic Brake Control Systems: Antilock Brake System (ABS), Traction Control System (TCS), and Electronic Stability Control System (ESC) Diagnosis and Repair |
04Questions by content area
Working on one part of the A5 test? Each content area has its own page with five more free questions.
05More free questions
The A5 study guide covers each content area and how to study for it, and the ASE A5 Brakes practice test page describes the full A5 question bank. The same free format is available for the other eight tests.
How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.
ToolboxPrep is an independent study site. It is not affiliated with or endorsed by ASE (the National Institute for Automotive Service Excellence). Our questions are original practice questions written to the published ASE test specifications; they are not actual test questions.