VW Transporter Brake Pedal Issues: Spongy & Vibrating

Having low experience with brake systems, I faced a similar issue with my 2011 VW Caddy last year. The symptoms started exactly like yours, spongy brake pedal and inconsistent feedback. Initially thought it was worn brake pads or brake rotors, but after taking it to the workshop, they diagnosed an electrical issue causing undervoltage in the brake control module. This affected the brake calipers performance and overall braking efficiency. The fix included recalibrating the control unit and replacing some wiring, costing 240€ in total. The disc brakes themselves were actually in decent condition, but the electrical problem was causing them to perform poorly. The repair took about 4 hours, and the braking has been perfect since then. To better assist with your specific case, could you provide: Any warning lights on the dashboard? When did you last have your brake fluid changed? Does the issue occur more when the engine is cold or warm? Have you noticed any electrical issues with other systems? The symptoms you describe could have multiple causes, and knowing these details would help narrow down whether you are facing a similar electrical issue or if its mechanical wear of the brake components.

After my last service at 59989km, the mechanic found the brake fluid was low and topped it up. However, the spongy pedal feeling returned after just a few days. The hydraulic brakes still show these symptoms regardless of engine temperature. No warning lights on the dash, but the squeaky brakes occur mostly during morning drives. The brake calipers seem to engage unevenly, the car pulls slightly to one side during hard braking. Will definitely check for electrical issues based on your experience, but suspect there might be air in the brake system. Thanks for sharing those repair costs. Will update once I get it diagnosed properly.

Thanks for the additional details. After reading about your brake fluid issues, this sounds remarkably different from my electrical problem, despite the similar symptoms in our VW Caddys. The combination of low brake fluid, squeaky brakes in the morning, and uneven brake caliper engagement strongly suggests air in your brake lines rather than an electrical fault. My mechanic explained that these are classic symptoms of a potential leak in the brake system, allowing air to enter. In my case, after the electrical fix, I actually developed a similar issue about 6 months later. It turned out to be a small leak at one brake caliper seal, which was allowing air into the system. The repair involved: Complete brake fluid flush, Replacing the faulty brake caliper seal, Bleeding all brake lines to remove air Total cost was around 320€ Given your symptoms, particularly the brake fluid loss and uneven braking, I would prioritize having the brake lines and calipers checked for leaks. The squeaky brakes in the morning could also indicate worn brake pads, but that's likely a secondary issue to the hydraulic problem. Just keep an eye on your brake fluid level, if it keeps dropping, definitely get it checked immediately. Low fluid combined with air in the lines can lead to complete brake failure.

Thanks everyone for the helpful replies. Just got back from the workshop and wanted to share the outcome of my brake system issues. Turns out you were right about the hydraulic brakes having air in the lines. The mechanic found a slow leak from a corroded brake line near the rear left wheel. The metal brakes and brake pads were actually in decent condition, but the air in the system was causing the spongy pedal feel and uneven braking. Final repairs included: Replacing the corroded brake line, Complete brake fluid flush, Full system bleeding Total cost came to 280€ The squeaky brakes turned out to be just some surface rust that cleared up after the repair. The pedal feels firm again and the car stops evenly now. Really glad I got this fixed before it became a bigger safety issue. Great advice about watching the brake fluid levels. Will definitely keep an eye on that from now on during regular maintenance checks.