freeasestudyguides Brakes 11-15

Which of the following brake fluids is silicon-based?

• Dot 5.1

• Dot 3

• Dot 4

• Dot 5

Answer explanation

Dot 5 is the only silicon-based brake fluid among the options. It is designed for high-performance applications and is not hygroscopic, unlike Dot 3, 4, and 5.1, which are glycol-based.

A vehicle has a low brake pedal that slowly fades to the floorboard. What is causing this condition?

• A faulty metering valve

• Leaking master cylinder cup seals

• Contaminated brake fluid

• Vacuum brake booster failure

Answer explanation

A low brake pedal that fades to the floor indicates a loss of hydraulic pressure, often caused by leaking master cylinder cup seals. This allows brake fluid to bypass, leading to a soft pedal feel.

The front of a passenger vehicle has a growling sound that increases in intensity while making left-hand turns. What is the MOST likely cause?

• Excessive rotor lateral run out

• A faulty right-front wheel bearing

• A faulty left-front wheel bearing

• A worn outer CV-Joint

Answer explanation

The growling sound during left turns suggests increased load on the right-front wheel bearing. A faulty right-front wheel bearing is likely to produce noise that intensifies when turning left, as weight shifts to that side.

The master cylinder reservoir cap gasket is swollen and deformed. Who is correct?

• Both A and B

• Technician B: Brake fluid is hygroscopic and absorbs moisture from the air.

• Technician A: This could be caused by contaminated brake fluid.

• Neither A or B

Answer explanation

Both technicians are correct. Technician A points out that contaminated brake fluid can cause gasket deformation, while Technician B correctly states that brake fluid absorbs moisture, which can also lead to swelling.

What is the main characteristic of DOT 5 brake fluid?

• Glycol-based

• Non-hygroscopic

• Silicon-based

• Hygroscopic

Answer explanation

DOT 5 brake fluid is silicon-based, which makes it non-hygroscopic, meaning it does not absorb moisture like glycol-based fluids. This characteristic helps prevent corrosion and maintains performance in braking systems.

What is a common symptom of a faulty brake booster?

• Low brake pedal

• Hard brake pedal

• Brake pedal pulsation

• Brake fluid leak

Answer explanation

A common symptom of a faulty brake booster is a hard brake pedal. This occurs because the booster is not providing the necessary assistance to the brake system, making it difficult to press the pedal.

What is the function of a metering valve in a brake system?

• To delay pressure to the front calipers

• To increase pressure to the rear brakes

• To balance pressure between front and rear brakes

• To release pressure from the brake system

Answer explanation

The metering valve's function is to delay pressure to the front calipers, ensuring that the rear brakes engage first. This helps maintain stability and control during braking, especially in vehicles with different brake sizes.

What is the effect of a warped rotor on a vehicle?

• Growling sound while turning

• Low brake pedal

• Pulsating brake pedal

• Hard brake pedal

Answer explanation

A warped rotor causes uneven contact with the brake pads, leading to a pulsating brake pedal when braking. This is the most common symptom, as the pedal vibrates due to the inconsistent surface of the rotor.