Examkin

Question

Difficulty: EasyBraking Systems

A motorist reports that the brake pedal feels spongy and travels excessively close to the floor before the brakes engage. What is the most likely cause of this condition?

  1. A
    Warped front brake rotors
  2. B
    Glazed friction linings on the brake shoes
  3. Air trapped within the hydraulic brake linesAnswer
  4. D
    A broken parking brake cable

Answer

Air trapped within the hydraulic brake lines
Hydraulic braking systems depend entirely on incompressible brake fluid to transfer force from the master cylinder to the wheel assemblies. If air enters the hydraulic lines, pressing the pedal compresses the trapped air bubbles before fluid pressure can actuate the brakes, resulting in a soft or spongy pedal feel with excessive travel.

Step-by-Step Solution

1
Identify the primary symptom described in the scenario
The symptom is a spongy, low-traveling brake pedal.
Accurate automotive diagnosis requires distinguishing between hydraulic faults and mechanical or friction component faults.
2
Analyze how fluid and gas behave under pressure in a closed hydraulic system
Brake fluid is virtually incompressible and immediately transfers applied force, whereas air is highly compressible.
When air is present in the hydraulic circuit, applying the brake pedal compresses the air bubbles instead of immediately pushing the caliper or wheel cylinder pistons, creating a spongy pedal feel.

Key Concept

Hydraulic Fluid Incompressibility and Brake Pedal Sponginess
Estimated Time:45s
Rate this question

Topics

Braking Systems

More questions from this topic