What is the main cause of the brake pedal feeling spongy or elastic when pressed?

Question

DentroTest · Accepted Answer

The correct answer is the presence of air in the system. Hydraulic brakes work because brake fluid is 'incompressible', transmitting force directly from your foot to the wheels. If air enters the brake lines, because air is a compressible gas, the force applied to the pedal is wasted compressing these bubbles instead of applying the brakes. This creates that 'springy' or spongy sensation and dangerously reduces braking efficiency. To fix this, the system must be 'bled' to remove the air. NOTE: Low fluid usually triggers a dashboard warning light, and overheated pads cause 'brake fade' (loss of friction), but the specific elastic symptom is the hallmark of air in the lines.

What is the main cause of the brake pedal feeling spongy or elastic when pressed?

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