Spongy RS7 Brakes Signal Potential Fluid or Line Issue

Had this exact issue on my 2020 RS6 Avant. The spongy brake pedal combined with increased pressure needed for braking typically points to air in the brake lines or low brake fluid levels. After inspection, my master cylinder was leaking brake fluid, causing air to enter the system. The brake lines themselves were intact, but the entire braking system needed a thorough brake fluid replacement and bleeding to remove trapped air. This is a serious safety concern that needs immediate attention. The RS models use a complex brake system, and any compromise in hydraulic pressure can lead to brake failure. My recommendation would be to check the brake fluid reservoir first, if its low or looks dirty, thats your first warning sign. The fact that your brake warning light hasnt illuminated yet doesnt mean you should wait. When I experienced this, the warning light only came on after the fluid level dropped significantly. These symptoms match classic signs of either a master cylinder issue or air in the brake lines. Get it checked immediately, these brake system issues dont fix themselves and typically worsen over time.

Thanks for following up on my original post about the RS7 brake issues. The mechanic found exactly what you suggested, a faulty master cylinder that was allowing air into the brake system. They had to replace it and do a complete brake fluid flush. Just wondering, what did the repair end up costing you? My total bill came to around 850 Euro including labor and parts. Also curious if youve had any other brake inspection issues since getting it fixed? The brake pedal feels firm now but want to make sure I stay on top of any potential problems with these performance brakes.

The repair cost on my RS6 was significantly lower at 480 Euro, which included fixing the worn brakes and addressing the brake fluid level issue. After the repair, the hydraulic brake system has performed flawlessly for the past 8 months. The brake pedal firmness returned immediately after they bled the system and replaced the fluid. Make sure to keep an eye on your brake fluid level through the reservoir, it should stay consistent now. If you notice any drop in fluid level, that could indicate a new leak in the system. Since the repair, I do a quick visual check of the brake fluid reservoir monthly. No issues have come up with the brake lines or hydraulic system. The pedal remains firm and responsive, exactly how it should feel in these performance models. The higher cost you paid might be due to regional labor rates or additional parts that needed replacement. The important thing is that your brake system is now properly serviced and safe.

Finally got my RS7 brake issue sorted and wanted to close out this thread. After the master cylinder replacement and brake fluid flush, the car drives like new again. You were spot on about the air in the brake lines, my mechanic found the old master cylinder had a small leak that was letting air into the system. The repair cost me 850 Euro, which seemed steep until I compared it with others. The brake pedal is back to its normal firm feel, and the braking response is exactly how it should be on these performance cars. Going to do regular brake inspections from now on and keep a close eye on the brake fluid level. Lesson learned about not waiting when brake issues first appear. Thanks again for helping me diagnose this, saved me from going back to that questionable shop that might have made things worse. Best part is having confidence in the brakes again. These performance models need proper maintenance, and skimping on brake system repairs isnt worth the risk.