Spongy SQ7 Brakes: Early Warning Signs to Watch

As someone with some brake repair experience, I had a very similar issue with my Q7 from 2020, sounds exactly like what you described. The spongy brake pedal and vibration were concerning symptoms that I initially thought were related to worn brake pads or brake rotors. After taking it to the workshop, they discovered an undervoltage issue affecting the brake system electronics. The problem was causing inconsistent hydraulic pressure in the brake calipers, leading to that spongy feel and unreliable braking performance. The complete diagnostic and repair, including fixing the electrical system, cost me 240 Euro. The squeaking in cold conditions might be a separate issue though, could be related to your brake shoes or brake pads needing adjustment. However, to provide more specific guidance, could you share: What year is your SQ7? Have you noticed any warning lights on the dashboard? Does the brake pedal feel different when the engine is cold vs warm? Are the vibrations constant or do they occur at specific speeds? This information would help determine if your issue matches what I experienced or if there might be other factors involved.

Thanks for checking, just updated my maintenance log. Last service was at 125000km, basically 3600km ago where they did a general inspection but no brake work. The vibrations mainly happen above 80km/h and get worse with harder braking. No warning lights on the dash yet. The spongy pedal feel is definitely more noticeable when the engine is cold and improves somewhat after driving for 15-20 minutes. The hydraulic brakes behave normally in terms of pressure needed to stop the car. Our brake pads still have decent thickness according to the last check, but the brake rotors have never been replaced since I got the car. Could worn brake rotors be causing these symptoms even with relatively new pads? The squeaking mostly happens after the car sits overnight.

Good to hear back from you. Based on the additional details, your symptoms actually sound different from the electrical issue I encountered. The fact that the vibrations occur at higher speeds and the pedal feel improves when warm points more toward mechanical wear rather than the hydraulic pressure problems I had. The symptoms you describe strongly suggest worn brake rotors, especially since they are original. When brake rotors wear unevenly or develop surface variations, they can cause vibrations that increase with speed and brake pressure. The cold weather squeaking is common with metal brakes when moisture collects on the rotors overnight. In my case, after fixing the electrical problem, I also ended up replacing my brake rotors at around 130000km because of similar vibration issues. The brake pads were still good, but the rotors had developed significant wear patterns. The repair involved: New brake rotors, Cleaning and lubricating the brake calipers, Fresh brake fluid flush Total cost was around 580 Euro and completely resolved both the vibration and cold weather noise. The brake pedal feel became much more consistent too. Would definitely recommend having your brake rotors inspected for uneven wear patterns or warping. These issues usually develop gradually, which explains why they become more noticeable at higher speeds.

Thanks for the detailed explanation. Your experience really helps put things in perspective, especially about the brake rotor wear patterns causing vibrations at higher speeds. Makes total sense given my brake rotors are original and have never been replaced. I just scheduled a workshop appointment for next week to have the entire brake system checked. Going to have them pay special attention to the brake rotors and consider replacing them even if the metal brakes are still within spec. The combination of vibrations, cold weather squeaking, and spongy pedal feel seems too similar to what you experienced to ignore. Quick follow-up, did you notice any significant improvement in general braking performance after getting the new rotors and brake fluid flush? Also wondering if 580 Euro is still a reasonable price range to expect for similar work these days? Just trying to budget appropriately for what might need to be done.