freeasestudyguides Brakes 56-60

A vehicle with a front disc, rear drum brake system skids and nosedives when the brakes are first applied. Which of the following is causing this condition?

• Aerated brake fluid.

• The proportioning valve.

• The metering valve.

• The pressure differential switch.

Answer explanation

The metering valve controls brake fluid flow to the front disc brakes, ensuring they engage before the rear drums. If it malfunctions, it can cause skidding and nosediving when brakes are applied, leading to the described condition.

The red brake warning light is illuminated on the instrument panel of a vehicle with four-wheel disc brakes. Which of these is LEAST likely to cause this warning light to illuminate?

• Grounded parking brake circuit.

• Unequal brake fluid pressure.

• Low brake fluid level.

• Loose wheel speed sensor plug.

Answer explanation

A loose wheel speed sensor plug is least likely to trigger the red brake warning light, as it primarily affects traction control and ABS, not the brake system itself. The other options directly relate to brake function.

The manufacturer recommends a burnishing procedure after replacing the vehicle's brake pads and rotors. Technician A says the procedure requires several hard, high-speed stops. Technician B says this process includes many light applications of the brake pedal and a brief cool-down period between stops. Who is correct?

• Both A and B

• Neither A or B

• Technician A

• Technician B

Answer explanation

Technician B is correct. The burnishing procedure involves light brake applications with cool-down periods to properly seat the new pads and rotors, rather than hard stops, which can lead to uneven wear.

Technician A says to use the scan tool's bidirectional function to test the bulb of an inoperative parking brake warning light. Technician B says a scan tool may be required to retract the piston of an electronic parking brake caliper before servicing the rear brakes. Who is correct?

• Technician A

• Technician B

• Both A and B

• Neither A or B

Answer explanation

Both technicians are correct. Technician A is right about using the scan tool's bidirectional function to test the bulb, and Technician B is correct that a scan tool is needed to retract the piston of an electronic parking brake caliper.

What does the pressure differential switch do in a brake system?

• Controls pressure to the rear brakes.

• Warns the driver of a possible hydraulic leak.

• Delays hydraulic pressure to the front brakes.

• Causes a spongy pedal.

Answer explanation

The pressure differential switch monitors brake fluid pressure. If it detects a significant difference, it alerts the driver to a potential hydraulic leak, ensuring safety by preventing brake failure.

What is the effect of aerated brake fluid in a brake system?

• Warns the driver of a possible hydraulic leak.

• Delays hydraulic pressure to the front brakes.

• Causes a spongy pedal.

• Controls pressure to the rear brakes.

Answer explanation

Aerated brake fluid introduces air into the brake system, which compresses under pressure. This results in a spongy pedal feel, making it harder for the driver to apply consistent braking force.

Which tool is used to retract the piston of an electronic parking brake caliper before servicing?

• A torque wrench.

• A hydraulic press.

• A bidirectional scan tool.

• A standard wrench.

Answer explanation

A bidirectional scan tool is specifically designed to communicate with the electronic parking brake system, allowing the piston to be retracted for servicing. Other tools listed do not serve this purpose.