Brake Systems and Safety Inspection Flashcards

A customer reports a pulsating brake pedal during moderate stops from highway speed. What is the most likely cause?

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.

A disc brake rotor measures below the 'MIN TH' dimension cast into it. What should the technician do?

Answer: Replace the rotor

A rotor below minimum thickness cannot absorb and get rid of heat safely and must be replaced, not machined.

Which brake fluid is silicone-based and must not be mixed with glycol-based fluids?

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.

A brake pedal feels spongy but firms up when it is pumped several times. What is the most likely cause?

Answer: Air in the hydraulic system

Air compresses under pedal force, which gives a spongy pedal that improves when pumped.

A vehicle pulls to the right during braking only. Which condition could cause this?

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.

On a disc/drum system, what is the purpose of the metering valve?

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.

What is the main function of a proportioning valve?

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.