DFFT Brakes and Braking Systems 3

Question 1

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

Accepted Answer

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

Answer

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

Question 2

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

Accepted Answer

The brake proportioning valve is faulty or maladjusted

Answer

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.

Question 3

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

Accepted Answer

Reduced friction and uneven contact, decreasing braking efficiency

Answer

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

Question 4

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

Accepted Answer

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

Answer

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

Question 5

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

Accepted Answer

A faulty wheel speed sensor sending erratic signals

Answer

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

DFFT - Driver Fault Finding Test Practice Test

DFFT - Driver Fault Finding Test Practice Test

DFFT Brakes and Braking Systems 3