Which condition contributes to spongy braking actions due to deterioration of hoses?

• A. Deterioration of the flexible brake lines
• B. Overheating
• C. Air in the system
• D. Contaminated fluid

Answer: (A)

Spongy braking action is caused by a loss of stiffness in the hydraulic path, so the brake pressure you build doesn’t translate immediately into brake force. When the flexible brake lines deteriorate, their walls soften, crack, or swell under pressure. That means part of your applied force goes into expanding the hose rather than into moving the brake components. The result is a pedal that sinks with little immediate braking response—a soft, spongy feel—because the pressurized fluid is being absorbed by the compromised hoses before it reaches the calipers or wheel cylinders. Over time, this deterioration can also trap moisture or debris, further degrading the system’s ability to transmit clean, instant pressure.

For context, other problems can cause related symptoms in different ways. Overheating causes brake fade rather than a spongy pedal. Air in the system creates a spongy feel because air is compressible, but that isn’t tied to hose deterioration. Contaminated fluid can inhibit braking performance too, but it doesn’t specifically describe deterioration of the hoses themselves.