Brake Systems & Suspension Flashcards

A brake pedal feels spongy but becomes firmer when pumped several times. What is the most likely cause?

Answer: Air trapped in the hydraulic system

Air compresses under pressure, so pumping temporarily stacks fluid volume and firms the pedal.

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

Answer: DOT 5

DOT 5 is silicone-based, while DOT 3, 4, and 5.1 are glycol-based and mutually compatible.

With steady foot pressure, the brake pedal slowly sinks to the floor, but no external leaks are found. What is the most likely cause?

Answer: Internal leak past the master cylinder piston seals

Worn master cylinder cups let fluid bypass internally, causing a slow pedal drop with no visible leak.

A vehicle pulls to the LEFT only when the brakes are applied. Which condition could cause this?

Answer: A collapsed right front brake hose

A restricted right front hose reduces right-side braking force, so the stronger left side pulls the vehicle left.

Excessive disc brake rotor lateral runout most commonly causes which symptom?

Answer: Brake pedal pulsation

Runout knocks the pads back, causing thickness variation over time that the driver feels as pedal pulsation.

What is the purpose of a proportioning valve?

Answer: Limit rear brake pressure to prevent rear wheel lockup

During hard stops weight shifts forward, so the proportioning valve reduces rear pressure to keep the rear wheels from locking.

On a disc/drum system, what does the metering valve do?

Answer: Holds off front disc pressure until the rear drum shoes overcome return spring tension

The metering valve delays front disc application so the front and rear brakes apply at nearly the same time.