Soft Brake Pedal & Low Fluid in Audi S8 Needs Fixing

Recently dealt with similar symptoms on my 2010 A8 4.2L. The spongy brake pedal combined with low brake fluid pointed to a leak in the brake system. During the brake inspection, the mechanic found deteriorated brake lines near the rear wheel wells. The metal lines had corroded due to exposure to road salt and moisture over time. This was a serious safety issue requiring immediate attention. The repair involved replacing several sections of brake lines, bleeding the entire hydraulic brake system, and installing new brake fluid. The worn brake components were showing signs of age rather than high mileage. For your S8, given the age and symptoms, its likely facing similar brake system issues. The spongy pedal feel often indicates air in the lines or a leak somewhere in the hydraulic system. This requires a thorough brake inspection focusing on: Brake line condition, especially near wheel wells and flex points, Master cylinder seals, Brake fluid quality and contamination, Caliper operation and seals Do not drive with a soft brake pedal, this significantly compromises stopping power and safety. Have it inspected as soon as possible by a qualified brake specialist.

Thanks for sharing your experience. I had almost identical symptoms with my S8 last year when the brake pedal started feeling soft. The warning light hadnt come on yet but the brake fluid was dropping steadily. Your situation sounds exactly like what I dealt with, my master cylinder was failing and allowing air into the brake system. Would be good to hear back how much the total repair ended up costing you? And has everything been working properly since the fix? With brake issues its always better to address them early before they turn into bigger problems requiring complete brake system overhaul.

Had the brake inspection done last week and everything is working perfectly now. The mechanic confirmed it was indeed very similar to your case, the brake fluid level low warning was due to a failing master cylinder letting air into the hydraulic brakes. The total repair came to 480 Euro which included replacing worn brakes components, a complete fluid replacement, and bleeding the brake system. While not cheap, the improvement in brake pedal feel and response was immediate and significant. The braking is now firm and predictable with no sponginess at all. Regular brake inspections are definitely worth it to catch these issues early, as waiting too long can lead to more extensive brake system repairs down the line. Its been about 1000km since the fix and the brake fluid level has remained stable with no signs of any leaks or air in the system. The investment in proper repair work really paid off in terms of safety and peace of mind.

Ended up taking it to a reputable brake specialist after seeing these responses. The diagnosis confirmed a failing master cylinder that was causing air to enter the hydraulic brakes. Had similar damage to the brake lines near the wheel wells due to corrosion. The total repair bill was 520 Euro which covered new brake lines, master cylinder replacement, brake fluid replacement and a complete system bleed. More than I initially hoped to spend but the brake pedal is now firm and responsive with no sponginess. The warning light issue turned out to be related to the low brake fluid caused by the leaking master cylinder. After the repair, all warning indicators cleared up. Really glad I addressed this early before facing a complete brake system failure. Its been two weeks since the fix and the brakes feel better than they have in years. No more having to press the pedal halfway down before getting proper stopping power. Definitely worth getting it done right by a qualified shop that specializes in hydraulic brake systems.