Brakes and Braking Systems Flashcards

During a DFFT test, a brake drum is found to be scored with deep grooves. What is the correct action?

Answer: Replace or machine the drum if within manufacturer's serviceable limits

Deep grooves reduce braking efficiency and can damage new shoes; the drum must be machined smooth or replaced if beyond its maximum inside diameter.

A rear-wheel-drive vehicle's rear brakes lock up before the front brakes under hard braking. What does this indicate?

Answer: The brake proportioning valve is faulty or maladjusted

The proportioning valve is designed to limit rear brake pressure to prevent rear wheel lockup; if it fails, too much pressure reaches the rear brakes.

A technician notices rust and pitting on the interior of a brake drum. What effect will this have on braking?

Answer: Reduced friction and uneven contact, decreasing braking efficiency

Pitting and rust create an uneven contact surface between the drum and shoes, reducing the effective friction area and causing inconsistent braking performance.

What does it mean when brake fluid has a dark brown or black color?

Answer: The fluid is old, contaminated, and has absorbed excessive moisture

Dark brake fluid indicates oxidation and high moisture content, which lowers the boiling point and can cause internal component corrosion and brake fade.

A vehicle's ABS activates during normal, non-emergency stops at low speed. What is the most likely cause?

Answer: A faulty wheel speed sensor sending erratic signals

An erratic or intermittent wheel speed sensor signal can falsely indicate wheel lockup to the ABS module, causing the system to activate unnecessarily.

After bleeding the brakes, the pedal remains soft. What should the technician check next?

Answer: Inspect all brake hoses for internal collapse or restriction

A collapsed inner lining in a flexible brake hose can act as a one-way valve, trapping pressure in the caliper and preventing complete fluid flow during bleeding.