Brake Systems Flashcards

What is the function of the electronic stability control (ESC) system during an oversteer condition?

Answer: It applies the outer front brake to create a corrective yaw moment that straightens the vehicle

During oversteer (rear sliding outward), ESC applies the outer front brake to create a yaw force opposing the spin, while simultaneously reducing engine power, helping the driver regain directional control.

What is the purpose of the brake pedal position sensor in vehicles with electronic brake systems?

Answer: To provide the brake control module with precise pedal travel and force data for calculating braking demand

The brake pedal position sensor (or force sensor) provides the electronic brake control module with precise data about how far and how fast the driver pushes the pedal, allowing accurate calculation of intended braking force.

What is the effect of using DOT 5 silicone brake fluid in a system designed for DOT 3/4?

Answer: Seal swelling or damage because silicone fluid is incompatible with the seals designed for glycol-based fluids, plus poor air absorption

DOT 5 silicone-based fluid is NOT compatible with systems designed for glycol-based DOT 3/4. It can cause seal swelling, is compressible when aerated, and does not absorb water (which then pools and causes localized corrosion).

What is the purpose of the traction control system (TCS)?

Answer: To prevent drive wheel spin during acceleration by reducing engine power and/or applying brakes to the spinning wheel

TCS uses wheel speed sensors to detect drive wheel spin. When spin is detected, it reduces engine torque (via throttle, fuel, or spark control) and/or applies the brake to the spinning wheel to transfer torque to the wheel with traction.

A vehicle has a low, slowly sinking brake pedal when held with constant pressure. There are no visible fluid leaks. What is the most likely cause?

Answer: An internal leak in the master cylinder past the primary piston seal

A sinking pedal with no external leaks indicates an internal master cylinder bypass. Fluid leaks past the worn primary cup seal from the pressure chamber into the reservoir, allowing the pedal to slowly sink to the floor.

What is the function of the automatic brake hold feature found in many modern vehicles?

Answer: To maintain brake pressure at the calipers after the driver releases the brake pedal at a stop, releasing when the accelerator is pressed

Automatic brake hold uses the ABS/ESC hydraulic modulator to maintain brake pressure at the wheels when the vehicle is stopped, even after the driver lifts off the brake pedal. It releases when the accelerator is pressed.