Spongy Audi S5 Brakes Signal Dangerous Fluid Loss

As an A4 2.0T owner from 2012, I encountered nearly identical brake system symptoms. The spongy brake pedal combined with low brake fluid strongly indicates either a leak in the brake lines or air in the system. My situation required immediate attention, driving with these symptoms risked complete brake failure. The warning signs matched yours exactly: pedal sinking deeper, sponginess, and low fluid level. The inspection revealed corroded brake lines that were slowly leaking fluid. The repair involved: Complete brake fluid replacement, Brake line inspection and replacement, Bleeding the brake system, Master cylinder testing, Full brake system pressure test While my master cylinder was functional, the leak in the brake lines was serious enough to compromise the entire brake system. These symptoms should not be ignored, they indicate a safety-critical issue requiring professional inspection. Your described symptoms suggest similar underlying issues. The brake warning light will likely activate soon if fluid levels continue dropping. Consider having a certified shop perform a thorough brake system diagnostic before continuing regular use of the vehicle.

Thanks for sharing your experience. Similar symptoms led me to a complete brake system overhaul on my S5. The brake pedal getting soft was definitely nerve-wracking. Really glad I caught it early. Just curious, do you remember the total repair cost for fixing the brake lines and fluid replacement? Also, have any other brake system issues popped up since the repair was done? Asking because I noticed my brake pedal starting to feel slightly different again recently, though not as bad as before. Want to compare notes to see if this is a common long-term issue with these models.

Following my prior post about my brake system issues, got the repairs completed last month and the brake fluid level is now perfect. The complete overhaul including labor came to 480 Euro, mainly due to worn brakes that needed replacement alongside the brake line work. Since the brake fluid replacement and system bleeding, the brake pedal response has been consistently firm, no more spongy feeling. My suggestion would be to get your brake pedal checked again if youre noticing changes. These brake systems are sensitive and even minor variations in pedal feel can signal developing issues. The key is catching these brake system problems early. Regular brake fluid checks and immediate attention to any pedal feel changes have helped prevent more serious issues in my case. The investment in proper repairs definitely beats risking brake failure.

After dealing with those scary brake issues, I finally got it sorted at a different shop. The hydraulic brakes needed a complete system flush and they found a small leak in one of the brake lines near the rear wheel. Total bill came to 390 Euro including parts and labor. The mechanic showed me the old brake fluid, it was definitely contaminated. They did a proper brake inspection and found the master cylinder was actually fine, just needed the lines fixed and a thorough fluid replacement. Been driving it for about 2 weeks now and the brake pedal feels solid again. No more spongy feeling or sinking. Going to stick with regular brake system maintenance from now on. Much rather catch these issues early than risk driving with questionable brakes again. The new shop documented everything they did and even showed me the problem areas. Way better experience than my last mechanic who just brushed off my concerns about the brake pedal feel.