Automobile & Light Truck Certification Test A5 BrakesHydraulic System Diagnosis and RepairEasy
A technician is diagnosing a spongy brake pedal feel that improves after several rapid pumps. Which of the following is the most likely cause?
- AWorn brake pads
- BAir in the hydraulic system
- CA seized caliper piston
- DA clogged master cylinder compensating port
Show answer & explanationAnswer & explanation
Correct answer: B. Air in the hydraulic system
A spongy brake pedal that improves with pumping is a classic symptom of air in the hydraulic system. Air is compressible, leading to the spongy feel, and pumping can temporarily build pressure.
Why the other options are wrong
- A. Worn brake pads lead to a low pedal or increased pedal travel, but not typically a spongy feel that improves with pumping.
- C. A seized caliper piston would typically cause a pull or drag, not a spongy pedal.
- D. A clogged compensating port would likely cause the brakes to drag or lock up, not a spongy pedal.
Air in Brake Lines
Air trapped within the hydraulic brake system, which is compressible and reduces braking efficiency, causing a spongy pedal feel.
- Causes spongy pedal
- Pedal can improve with pumping
- Requires bleeding to remove
Memory trick: Spongy pedal, pump it up, air's the culprit, clear it out!