A soft or spongy brake pedal usually points to air in the brake lines, old or contaminated brake fluid, or a developing leak in the hydraulic system. Worn components or a failing master cylinder can also cause it. Because a spongy pedal directly affects stopping ability, it should be inspec t ed promptly to maintain a firm, reliable braking response.

Your braking system relies on hydraulic brake fluid to transfer the force from your foot on the pedal to the calipers that press the brake pads against the rotors. Fluid can not be compressed, which is what makes the force transfer fast and firm. Air, however, is compressible, so when air enters the brake system, some of your brake pedal effort gets "absorbed" by compressing that air bubble instead of activating the brakes. The result is a pedal that feels soft, mushy, or that travels farther than usual before the brakes engage.

Here is what typically causes air to get in and what else might be going on.

Air usually enters the system through a brake fluid leak, a failing brake caliper seal, a rusted brake line, or a deteriorating rubber brake hose. Over time, brake fluid also absorbs moisture from the air, lowering its boiling point and causing it to partially vaporize under hard braking, creating an air bubble — a source of compression in the system. This is one reason why brake fluid replacement on a schedule is often overlooked in vehicle maintenance.

Less commonly, a failing master cylinder, the component that generates hydraulic pressure when you press the pedal, can create a similar spongy sensation without an obvious fluid leak. If the internal seals in the master cylinder are worn, they cannot hold pressure properly.

A spongy pedal is not a warning to ignore. If the underlying leak worsens, pedal feel and braking power can deteriorate further.

Hoover Street Auto Repair in Ann Arbor can bleed your brake system, locate any leaks, and restore the firm, responsive pedal feel your Jeep should have.

See our general brake repair page for more information about our brake service.

Why does my Jeep brake pedal feel soft or spongy?

Here is what typically causes air to get in and what else might be going on.