Spongy Audi A5 Brakes Signal Dangerous Hydraulic Issues

I had a similar issue with my 2012 Audi A4 2.0T last year. Having some experience with basic brake maintenance, I first thought it was related to the brake shoes or disc brakes, but it turned out to be more complex. After noticing the inconsistent brake pedal behavior, I took it to my regular workshop. They diagnosed an undervoltage problem affecting the brake system electronics, particularly the ABS module. The squeaky brakes and spongy pedal were symptoms of the electrical system not properly maintaining the right voltage for the brake assist functions. The total repair came to 240 Euro, which included diagnostic work and fixing the voltage regulator. Since then, the brake rotors and pedal response have been working perfectly normal. Before suggesting specific solutions for your A5, it would be helpful to know: Are there any warning lights on the dashboard? Does the issue occur more when the engine is cold or warm? Have you noticed any other electrical issues like dimming headlights? When was the last time you had the battery checked? These details would help determine if your issue is similar to what I experienced with my A4 or if its something different with your metal brakes system.

Last service was at 132000 KM, and I am getting increasingly worried about the hydraulic brakes issue. Thanks for sharing the details about the voltage regulator. No warning lights showing on the dashboard. The brake pedal feels particularly spongy during cold starts but improves slightly when warm. Have not noticed any electrical issues or dimming lights. Battery was replaced 8 months ago and is working fine. Planning to get it checked next week but wanted to gather some insights from the community first.

Since we're talking about similar Audi models, let me share some follow-up thoughts based on your latest details. The symptoms you describe, especially the cold start sponginess that improves when warm, actually points to a different issue than what I experienced with my voltage regulator. The behavior suggests potential air in the brake lines or deteriorating brake fluid. Given your mileage (132000 KM) and the fact that the brake pads were done 40k miles ago, its time to consider a full brake system inspection. In my case, after fixing the voltage issue, I also had the brake fluid flushed as preventive maintenance. Air in the brake lines can cause similar symptoms, and brake fluid typically needs changing every 2 years regardless of mileage. The good news is that since your battery is new and there are no warning lights, we can likely rule out electrical issues. Focus your mechanic's attention on: Brake fluid condition and potential air in lines, Brake master cylinder condition, Brake rotors thickness measurement, Brake calipers for smooth operation Given the age of your A5, these components might need attention even if they arent the primary cause of your current issue. When my brake system was fully serviced after the voltage fix, the total cost including new brake fluid was around 180 Euro.

Thank you for the detailed feedback about the brake fluid and potential air in the lines. Your suggestion about cold start behavior makes a lot of sense. I will definitely have the mechanic check those specific components you mentioned, especially the brake master cylinder and brake calipers. My main concern was a major system failure, but it sounds like this could be resolved with proper maintenance and fluid replacement. Given that its been over 2 years since the last brake fluid change, that could explain the spongy pedal feel. I will request a complete inspection of the hydraulic brakes system and the brake rotors when I take it in next week. The 180 Euro cost reference for a full service is helpful for budgeting. At 132000 KM, investing in preventive maintenance seems smarter than waiting for a more serious issue to develop. Will report back after the inspection to share what they find, as it might help others with similar brake pedal issues on these models.