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Question

Difficulty: HardBraking Systems

A technician discovers that a single front disc brake caliper remains locked and overheats after the brake pedal is released. Which of the following is the most likely cause?

  1. A
    A leaking wheel cylinder piston cup
  2. B
    A broken brake shoe return spring
  3. An internally deteriorated flexible brake hoseAnswer
  4. D
    A worn rear differential pinion seal

Answer

An internally deteriorated flexible brake hose
Internal breakdown of a flexible rubber brake hose can form an internal restriction or flap that acts like a one-way check valve. While master cylinder pressure easily forces fluid through the hose to apply the caliper, the low pressure of releasing the pedal cannot overcome the flap, trapping fluid in the caliper and causing continuous drag and overheating.

Step-by-Step Solution

1
Analyze the reported symptom and system architecture
The symptom is localized to a single front wheel equipped with a disc brake caliper that fails to release pressure.
Isolating the issue to one wheel rules out central hydraulic components like the master cylinder or power booster, which affect multiple wheels.
2
Evaluate hydraulic and mechanical causes of single caliper lockup
When a flexible rubber brake hose deteriorates internally, a piece of rubber can act as a check valve, allowing high pedal pressure to enter the caliper but preventing fluid return.
Brake fluid must flow freely in both directions through the flexible line to permit prompt caliper piston retraction when the pedal is released.

Key Concept

Hydraulic restriction in flexible brake hoses causing caliper lockup
Estimated Time:1m 0s
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Topics

Braking Systems

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