Five free practice questions on brake hydraulics, power assist and parking brakes: content area A of the ASE A5 Brakes test, 19 of its 45 scored questions (42.2%). They are in the ASE format: four options, one best answer. Answer each one before opening the explanation. No account, no email.
01The questions
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Why is a quick take-up master cylinder used with low-drag disc brake calipers?
- It limits rear pressure during hard stops to keep the rear wheels from locking.
- It holds residual pressure in the calipers to keep the pads against the rotors.
- It raises the maximum line pressure at the front calipers in hard stops.
- It moves a large volume of fluid early in the stroke to take up pad clearance.
Show the answer
D. Correct. Low-drag calipers pull the pistons and pads farther from the rotor to cut drag, which takes extra fluid to close. The quick take-up design uses a large-diameter rear bore to push that volume early in the stroke, then its valve vents the excess to the reservoir so normal pressure builds.
Why not the others
A. Limiting rear pressure in hard stops is done by a proportioning valve or the ABS, not the master cylinder. The quick take-up feature acts at the start of the stroke, moving extra fluid to close the larger clearance of low-drag calipers.
B. Residual pressure in a disc circuit would make the pads drag, which is the opposite of what low-drag calipers are designed for. The quick take-up feature supplies extra volume early in the stroke to close the larger pad clearance.
C. A quick take-up design does not raise peak pressure; once the pad clearance is taken up, the excess fluid from the large bore is vented and pressure builds in the normal way. Its job is the extra volume at the start of the stroke.
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A new master cylinder is being bench bled before installation. Technician A says it should be held in a vise by its mounting flange rather than clamped across the body. Technician B says the ends of the bleeder tubes should stay below the fluid surface in the reservoir. Who is right?
- A only
- B only
- Both A and B
- Neither A nor B
Show the answer
C. Correct. Technician A is right because clamping across the body can distort the bore or damage an aluminum casting, so the flange is the place to hold it. Technician B is right because the tube ends must stay under the fluid so each return stroke draws fluid, not air, back into the bore.
Why not the others
A. Technician A is right, but so is Technician B. Holding the unit by its flange avoids distorting the bore, and keeping the tube ends submerged stops the pistons from drawing air back in on each return stroke.
B. Technician B is right, but so is Technician A: clamping across the body can distort the bore or crack an aluminum body, so the unit is held by its mounting flange. Submerged tube ends keep air from being drawn back in as the pistons return.
D. Both technicians are right. Technician A's flange mounting protects the bore from distortion, and Technician B's submerged tube ends keep air from being drawn back into the bore as the pistons return.
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A rear-wheel-drive car with front discs and rear drums locks its rear wheels in hard stops on dry pavement. The rear shoes and drums are new, clean and correctly adjusted, and the car has a fixed (non-load-sensing) proportioning valve. Which of these could be the cause?
- A proportioning valve not limiting rear pressure
- A metering valve that does not hold off front pressure
- A rear wheel cylinder piston seized in its bore
- A rear brake hose that is restricted inside
Show the answer
A. Correct. In a hard stop weight shifts forward, so the proportioning valve cuts the rate at which rear pressure rises above its split point to keep the lightly loaded rear wheels from locking. A valve that passes full pressure lets the rear brakes lock early; it is pressure tested and replaced.
Why not the others
B. The metering valve works at the start of a stop, holding off the front calipers until the rear shoes apply. It does not control rear pressure in hard stops, so it cannot make the rear wheels lock.
C. A seized wheel cylinder affects only its own wheel and cannot apply its shoe harder in a hard stop: stuck in place, it either weakens that brake or, if stuck out, makes it drag all the time. Lockup of both rear wheels in hard stops points to too much rear pressure.
D. A restricted rear hose slows and reduces the pressure reaching the rear brakes, which would make them weaker, not lock them. Rear lockup with good linings points to too much rear pressure from the proportioning valve.
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After a caliper replacement and bleed, any of these could leave air in the hydraulic system EXCEPT:
- tapping the caliper body lightly with a soft mallet while bleeding.
- letting the reservoir level fall low enough to uncover an outlet port.
- releasing the pedal before the bleeder screw is closed during manual bleeding.
- mounting the calipers on the wrong sides so the bleeder screws point down.
Show the answer
A. Correct. Light taps on the caliper while fluid flows help free bubbles that cling to the bore and passages, so the practice removes air rather than adding it. Air stays behind when it is let in or when the bleeder is not at the caliper's highest point.
Why not the others
B. This could leave air: once an outlet port is uncovered, the master cylinder draws air in and pushes it into the lines, and the bleed must be redone. The reservoir is kept topped up throughout.
C. This could leave air: as the pedal returns with the bleeder open, the caliper can draw air back in through the bleeder. The bleeder is closed before the pedal is released on each stroke.
D. This could leave air: a bleeder at the bottom cannot let out the air that collects at the top of the caliper. Calipers made for one side are mounted on that side so the bleeder sits at the highest point.
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On a pickup with a hydro-boost brake booster, both brake pedal effort and steering effort are high at idle and become normal above about 1,500 rpm. The drive belt squeals when the steering is turned to full lock, and the power steering fluid is full and free of foam. Which of these is the most likely cause?
- Air in the power steering and hydro-boost fluid
- A leaking hydro-boost accumulator
- A slipping power steering pump drive belt
- A master cylinder with a bypassing piston cup
Show the answer
C. Correct. Hydro-boost takes its pressure from the power steering pump, so anything that cuts pump output raises both brake and steering effort. A belt that squeals under the heavy load of full lock and gives normal assist at higher speed is slipping; the belt and tensioner are inspected and replaced as needed.
Why not the others
A. Air in the fluid shows as foam or a whine, and this fluid is full and free of foam. The shared high effort at idle with a squeal at full lock points to a slipping belt.
B. The accumulator only supplies reserve assist when pump flow stops, such as with the engine off; it does not affect steering effort. High brake and steering effort together at idle, with a squeal, point to the belt.
D. A bypassing master cylinder makes the pedal sink; it does not raise pedal effort, and it cannot affect steering. Both efforts rising at idle point to the belt driving the power steering pump.
02Answer key
| Question | Answer |
|---|---|
| Q1 | D |
| Q2 | C |
| Q3 | A |
| Q4 | A |
| Q5 | C |
03What area A covers
This content area covers the hydraulic side of the brake system and the parts that assist or hold it: the master cylinder, steel lines and flexible hoses, the valves and switches in the lines, brake fluid, bleeding and flushing, vacuum, hydro-boost and electro-hydraulic power assist, and cable and electronic parking brakes, along with the brake warning and stop lamp circuits.
The ASE test specification calls this content area “Hydraulic, Power Assist, and Parking Brake Systems Diagnosis and Repair”. It carries 19 of the 45 scored questions, 42.2% of the test.
- Trace pedal and stopping faults to the master cylinder
- Set booster pushrod length and bench bleed master cylinders
- Inspect, replace and flare brake lines and hoses
- Test metering, proportioning and pressure differential valves
- Check warning lamps, stop lamp switches and their circuits
- Choose brake fluid, then bleed, flush and pressure test
- Test vacuum, hydro-boost and electronic power assist
- Adjust and repair cable and electronic parking brakes
04What the questions turn on
A pushrod that is too long
An output pushrod adjusted too long holds the master cylinder cups over the compensating ports. Fluid that expands with heat cannot return to the reservoir, so pressure builds and all four brakes drag. Loosening the master cylinder lets the wheels turn freely.
Metering and proportioning are different jobs
The metering valve holds off front caliper pressure until the rear shoes reach the drums. The proportioning valve limits how fast rear pressure rises in a hard stop. Rear wheels locking early in hard stops points to the proportioning valve.
Hard pedal or soft pedal
Air compresses, so air in the hydraulic system makes the pedal soft and long, not hard. A hard pedal points to lost power assist, such as a failed vacuum pump or a slipping belt on a pump that feeds a hydro-boost unit.
What the fluid tells you
Glycol fluid absorbs moisture, which lowers its boiling point, so a pedal that goes soft after long braking and recovers when cool points to the fluid. Purple fluid means silicone DOT 5 was added. Swollen rubber and an oily smell mean petroleum contamination.
05The other content areas
The A5 test has four content areas. Each has its own page of free questions:
The ASE A5 Brakes practice test page describes the full question bank. 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.