NAPA Brake System Service 2

Question 1

What is a typical maximum allowable lateral runout for a disc brake rotor measured with a dial indicator?

Accepted Answer

0.002 in (0.05 mm)

Answer

Most manufacturers limit rotor lateral runout to about 0.002 in, since more causes thickness variation and pedal pulsation.

Question 2

Which condition is most likely to cause a vehicle to pull to one side only when the brakes are applied?

Accepted Answer

Grease-contaminated pads on one front wheel

Answer

Contaminated linings on one side reduce friction there, creating unequal braking force side to side.

Question 3

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

Accepted Answer

DOT 5

Answer

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

Question 4

A customer complains of a soft, spongy brake pedal that improves slightly when pumped. What is the most likely cause?

Accepted Answer

Air in the hydraulic system

Answer

Air compresses under pressure, producing a spongy pedal that firms up somewhat with pumping.

Question 5

When testing a vacuum brake booster, the engine is off, the pedal is pumped to deplete reserve, and then held while the engine is started. What should the pedal do?

Accepted Answer

Drop slightly toward the floor

Answer

A working booster applies assist as vacuum builds, so the pedal moves down slightly under steady foot pressure.

NAPA - National Automotive Parts Association Certified Mechanic Practice Test

NAPA - National Automotive Parts Association Certified Mechanic Practice Test

NAPA Brake System Service 2