RS3 Brake Booster Sensor Causing Poor Pedal Response

Had similar issues on a 2014 S3 after a routine brake service. The symptoms matched exactly, harder pedal feel and reduced brake performance. Initial diagnosis pointed to the brake booster, but the real problem was incorrect bleeding of the hydraulic brakes. The brake system required a complete professional re-bleeding using proper diagnostic equipment. Air bubbles in the hydraulic lines caused inconsistent brake pressure and triggered warning lights. This was a serious safety concern requiring immediate attention. A thorough inspection revealed the master cylinder was functioning correctly, but air had entered the system during previous service work. The ABS module required specific bleeding procedures using manufacturer-approved diagnostic tools to ensure all air was removed from the brake system. While brake booster pressure sensors can fail, its worth checking the simpler issues first. Proper bleeding of the brake system restored normal pedal feel and brake performance. The repair took about 4 hours including diagnostic time. For accurate diagnosis, recommend having a certified shop perform a complete brake system evaluation using proper diagnostic equipment rather than relying on general symptoms.

Thanks for the detailed reply about the brake system issues. Your experience matches what I went through with my RS3. After taking it to another shop, they also found air in the lines was the main culprit affecting vehicle safety and performance. Just curious, do you remember the repair costs for your brake service? Mine ended up needing a new brake pedal pressure sensor too a few months later, so wondering if thats a common follow-up issue with these models. Really helps to hear others experiences with similar problems.

I got my brake system issues fully resolved for 90 Euro at a specialist shop. The repair involved a complete system bleed using professional diagnostic tools to remove all trapped air. You mentioned your brake booster pressure sensor failing later, thats interesting because mine actually needed replacement too about 2 months after the initial fix. The sensor failure symptoms returned briefly, but replacing that component solved it permanently. The brake performance has been perfect since then. Looking back, the air in the lines probably stressed the pressure sensor, leading to its eventual failure. Its pretty common for these sensors to need replacement after brake system problems, especially when the original issue involved incorrect bleeding procedures. At least the initial diagnosis about trapped air was spot on. Getting the right diagnostic tools and proper bleeding technique made all the difference for restoring normal brake operation and safety.

Thanks everyone for the helpful insights. Let me share how my situation got resolved. After getting frustrated with my original mechanic, I found a certified shop specializing in brake systems. Their diagnostic tools quickly identified air in the brake lines as the main problem, confirming what others mentioned here. The complete brake system bleeding cost 120 Euro and took about 3 hours. The technician used proper equipment to ensure all air was removed, instantly improving the brake pedal feel and overall vehicle safety. Just as predicted, my brake booster pressure sensor failed two months later. The replacement part and labor added another 180 Euro to the total repair cost. But since fixing both issues, the braking performance has been perfect with no more dashboard warnings. Lesson learned, find a shop with the right diagnostic tools and expertise for brake system problems. Proper diagnosis saved me from unnecessarily replacing more expensive parts. The whole experience showed how important professional brake service is for vehicle safety.