ASE Brake Systems and Safety Inspection 2 — Questions and Answers
Question 1: A customer reports a pulsating brake pedal during moderate stops from highway speed. What is the most likely cause?
- Glazed rear drum shoes
- Excessive rotor thickness variation (Correct answer)
- Air trapped in the rear brake lines
- A weak master cylinder return spring
Correct answer: Excessive rotor thickness variation
Rotor thickness variation (often caused by lateral runout) makes the caliper pistons move in and out, which the driver feels as pedal pulsation.
Question 2: A disc brake rotor measures below the 'MIN TH' dimension cast into it. What should the technician do?
- Install thicker brake pads to compensate
- Replace the rotor (Correct answer)
- Reuse it if there is no visible scoring
- Machine it lightly and reinstall it
Correct answer: Replace the rotor
A rotor below minimum thickness cannot absorb and get rid of heat safely and must be replaced, not machined.
Question 3: Which brake fluid is silicone-based and must not be mixed with glycol-based fluids?
- DOT 4
- DOT 3
- DOT 5 (Correct answer)
- DOT 5.1
Correct answer: DOT 5
DOT 5 is silicone-based and does not mix with the glycol-based DOT 3, DOT 4, and DOT 5.1 fluids.
Question 4: A brake pedal feels spongy but firms up when it is pumped several times. What is the most likely cause?
- A leaking vacuum booster check valve
- A seized caliper piston
- Air in the hydraulic system (Correct answer)
- A restricted brake hose
Correct answer: Air in the hydraulic system
Air compresses under pedal force, which gives a spongy pedal that improves when pumped.
Question 5: A vehicle pulls to the right during braking only. Which condition could cause this?
- An overfilled master cylinder reservoir
- A seized caliper slide pin on the right front
- A seized caliper slide pin on the left front (Correct answer)
- A faulty brake light switch
Correct answer: A seized caliper slide pin on the left front
If the left front caliper cannot apply fully, the right side brakes harder and the vehicle pulls right.
Question 6: On a disc/drum system, what is the purpose of the metering valve?
- To delay front disc application until the rear shoes contact the drums (Correct answer)
- To keep residual pressure in the disc brake lines
- To limit rear brake pressure during hard stops
- To warn the driver of a hydraulic imbalance
Correct answer: To delay front disc application until the rear shoes contact the drums
The metering valve holds off front pressure until rear drum shoes overcome their return springs, which gives balanced braking on light stops.
Question 7: What is the main function of a proportioning valve?
- To boost front brake pressure on hard stops
- To return fluid to the reservoir when the pedal is released
- To equalize pressure between the left and right wheels
- To reduce rear brake pressure and prevent rear wheel lockup (Correct answer)
Correct answer: To reduce rear brake pressure and prevent rear wheel lockup
Weight shifts forward during braking, so the proportioning valve limits rear pressure to keep the rear wheels from locking first.
ASE Brake Systems and Safety Inspection 2
A customer reports a pulsating brake pedal during moderate stops from highway speed.
What is the most likely cause?