A5 Brakes — practice test
A5 Brakes is the ASE automobile test covering hydraulics, drums, discs, power assist, wheel bearings, parking brake, and ABS/traction/stability. It has a reputation as an easy test, and that reputation is exactly why techs walk in cold and walk out short. The failures are not on pad slaps - they are on hydraulic theory, master cylinder diagnosis, valve function, and knowing what a scan tool actually tells you about an ABS fault versus what the pedal is telling you.
Studying for A5 (Brakes)? Overhaul Prep has 122 verified A5 questions written to the current task list — in the same formats the real exam uses (direct, Technician A/B, EXCEPT and most-likely-cause). Every answer comes with a written explanation, so you learn why instead of memorising a letter.
What's on the A5 test
Roughly 45 scored questions plus unscored pretest items, about an hour. The task areas are hydraulic system diagnosis and repair (master cylinder, lines, hoses, valves, bleeding - the largest single block), drum brakes, disc brakes, power assist units, wheel bearings and related hardware, parking brake, and electronic brake control systems (ABS, traction control, stability). Disc and hydraulic together carry most of the weight. ABS/electronic is a real block now, not a token two questions. Expect a heavy dose of diagnosis-style items over pure R and R.
High-yield A5 topics
The material that shows up year after year. If you're short on time, start here.
- Master cylinder diagnosis: pedal slowly sinking to the floor with no external leak and a full reservoir means internal bypass past the cups - replace the master. Know the difference between that and a pedal that goes low then holds (air or adjustment). Know why you bench bleed and why fluid squirts in the reservoir on apply with a bad compensating port.
- Valves and warning lights: metering valve holds front discs off until rears develop pressure on front-disc/rear-drum vehicles, proportioning valve limits rear pressure to prevent rear lockup, pressure differential switch trips the red BRAKE light on a split-circuit imbalance. Techs mix up metering and proportioning constantly and the test knows it.
- Brake fluid: DOT 3, 4, and 5.1 are glycol based and hygroscopic; DOT 5 is silicone, not compatible, and not used with ABS. Know dry vs wet boiling point, why moisture gives you a spongy pedal after hard use, and why you never top off from an open can.
- Disc specifics: rotor thickness gets measured with a micrometer against the minimum/discard spec cast or stamped on the rotor, lateral runout with a dial indicator. Thickness variation (DTV, often only 0.001 in) causes pedal pulsation; an out-of-round drum does the same in drums. Seized caliper slides or pins give uneven inboard/outboard pad wear.
- ABS: passive AC reluctor sensors put out AC voltage whose frequency rises with speed - check with a meter or scope, check air gap and the tone ring for damaged teeth. Active sensors need supply voltage. Many systems require a scan tool to cycle the pump and valves to bleed, and pedal pulse plus noise during a hard ABS stop is normal operation, not a fault.
- Wheel bearings and hardware: serviceable tapered roller bearings get torqued while rotating, then backed off to the specified preload or end play - never just cranked down. Bearing noise changes with load on a sway test, and a failing hub bearing on an ABS car can set a wheel speed sensor code because the sensor lives in the hub.
Where techs lose points on A5
Good technicians miss these — not from lack of skill, but because the question is built to catch them.
- Low pedal that gradually sinks under steady foot pressure with no visible leak: the tempting answer is air in the system or worn pads. It is the master cylinder bypassing internally. Air gives you a spongy pedal that pumps up, not a slow sink.
- Rear lockup or a pull question and everyone reaches for the proportioning valve. Read the vehicle: on a front-disc/rear-drum car a stuck metering valve gives grabby fronts on light stops, and lockup can just as easily be contaminated linings, a seized wheel cylinder, or a collapsed hose acting as a check valve.
- Pulsation vs pull vs noise. Pedal pulsation is rotor DTV or a drum out of round. Steering wheel shimmy under braking points at the front rotors. A pull points at a hydraulic restriction, seized caliper, or one-side contamination - not thickness variation. Do not answer 'warped rotor' just because you say it in the bay; ASE wants the measured cause.
- Vacuum booster tests: 'replace the booster' is usually the wrong answer. Deplete the reserve with the engine off, hold pedal pressure, start the engine - if the pedal does not drop slightly, check the check valve, hose, and vacuum source first. A hard pedal with good vacuum is often a restricted check valve or an engine vacuum problem, not the diaphragm.
A study plan that works for A5
Roughly two weeks of real preparation, in the order that actually builds on itself.
- Days 1-4: Hydraulics until it is automatic. Master cylinder failure modes, split systems, metering/proportioning/differential valves, fluid types and boiling points, hoses vs lines, manual/pressure/vacuum/gravity bleeding and when each is required. Biggest block, and it feeds every other section.
- Days 5-7: Discs and drums with the measurement specs in hand. Micrometer and dial indicator use, minimum thickness vs machine-to spec, DTV and runout numbers, drum diameter limits, self-adjuster and duo-servo operation, caliper slide and piston service, and why rear-disc parking brake adjustment matters.
- Days 8-10: Power assist, wheel bearings, parking brake, then ABS/traction/stability. Booster test sequence, hydro-boost basics, bearing preload procedure, passive vs active wheel speed sensor testing, scan-tool-required bleeds, and what normal ABS activation feels like.
- Days 11-14: Practice tests only, timed. Then go back and write down WHY each wrong answer was wrong - if you cannot state the failure mechanism in one sentence, you do not know it. Re-drill hydraulics the day before; that is where the points are.
Sample A5 questions
Straight from the bank — answers highlighted, with the explanation underneath.
Which of the following brake fluids is silicone-based, does NOT absorb moisture, and must NOT be used in a vehicle equipped with an anti-lock brake system (ABS)?
- DOT 3
- DOT 4
- DOT 5
- DOT 5.1
Two technicians are discussing hydraulic control valves. Technician A says the metering valve delays hydraulic pressure to the front disc brakes until the rear drum shoes overcome their return springs, balancing front-to-rear application. Technician B says the proportioning valve reduces pressure to the rear brakes during hard stops to help prevent rear-wheel lockup. Who is correct?
- Technician A only
- Technician B only
- Both Technicians A and B
- Neither Technician
With the engine running and steady foot pressure applied, the brake pedal slowly sinks toward the floor, yet there are no visible external fluid leaks. Which is the MOST likely cause?
- Internal leakage — fluid bypassing the master cylinder piston cups
- Air trapped in the brake lines
- Glazed brake linings
- A stuck-open metering valve
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