VW Lupo's Brake Pedal Pulsation Needs Expert Diagnosis

I had a similar issue with my 2006 VW Polo diesel. Having some experience with brake systems, I first thought it was related to the brake rotors or calipers, but it turned out to be an electrical issue causing undervoltage in the vehicle, which affected the hydraulic brake system. The symptoms were identical, spongy brake pedal and pulsating feedback, especially when applying moderate pressure to the metal brakes. The workshop diagnosed it using their diagnostic equipment and found the voltage issue was impacting the brake system performance. The fix cost 240€ and included: Full electrical system diagnostic, Voltage regulator replacement, Brake system inspection, Test drive verification Before suggesting specific solutions for your Lupo, it would help to know: Current mileage? When was the last brake service performed? Are there any warning lights on the dashboard? Does the issue occur more when the engine is cold or warm? While the symptoms sound similar, having these details would help determine if your issue is electrical like mine was or if its actually related to worn brake components. The spongy feeling could also indicate air in the brake lines or worn brake shoes that need attention.

Last service was in February this year and my current mileage is 107272km. No warning lights showing on the dashboard. The issue happens regardless of engine temperature. After reading your experience, I checked the electrical system, but voltage readings are normal. The brake pedal pulsation feels more mechanical, like it is coming directly from the brake rotors or brake calipers when engaged. The vibration clearly increases with speed, which makes me lean towards a mechanical rather than electrical issue. The hydraulic brakes still work, but that pulsating sensation is concerning. Going to schedule a proper inspection focusing on the brake components. Thanks for sharing your experience, helps rule out the electrical system at least.

Makes sense that you ruled out electrical issues since the symptoms do point more towards mechanical wear. After dealing with my Polo's electrical problems, I later experienced similar mechanical pulsations that turned out to be warped brake rotors. The speed-dependent vibration through the brake pedal is a classic sign of uneven disc brakes. My rotors had developed varying thickness across their surface, causing that pulsating feedback when applying the brakes at higher speeds. The fix involved: Replacing front brake rotors (380€), New brake pads (120€), Brake fluid flush and refill Total repair came to about 650€ including labor. Could have been cheaper but I opted for OEM parts since the brake system is not something to compromise on. Worth checking the brake calipers too, sometimes they can stick partially, causing uneven wear on the rotors. At your mileage, its also smart to inspect the brake fluid condition since contaminated fluid can affect brake performance. Given the similarity of symptoms and the fact electrical issues are ruled out, I would bet your Lupo has the same warped rotor problem I encountered. A proper inspection should confirm this.

Thanks for the detailed feedback about warped rotors. Your repair cost breakdown is really helpful. Just booked the Lupo in for next Tuesday at my local workshop. Mentioned the symptoms and they also suspect warped brake rotors. Makes total sense given how the vibration increases with speed. Asked them to do a full brake system inspection including the brake calipers and hydraulic brakes while they have it up on the lift. The quote they gave me was around 700€ for potential rotor and brake pad replacement, which seems in line with what you paid. Good call on checking the brake fluid too, will have them look at that during the inspection. Better to address all brake-related issues at once rather than having to go back later. Will update once I know what they find.