Smart ForFour EV Spongy Brake Pedal Issues Fixed

Having some experience with electric vehicles and their brake systems, I encountered a very similar issue with my 2019 Smart ForTwo EV. The symptoms you describe with the brake pedal feedback match what I experienced. Initially I also thought it was related to worn brake pads, but when I took it to the workshop, they discovered an undervoltage issue affecting the brake system electronics. This was causing inconsistent hydraulic brake pressure distribution. The disc brakes themselves were in good condition, but the electronic brake force distribution wasnt working properly due to the voltage problem. The repair involved recalibrating the brake system and replacing a faulty voltage regulator component. Total cost was 240€ and solved the spongy pedal feel completely. Before jumping to conclusions though, could you share: Current mileage on your ForFour? When was your last brake fluid change? Does the issue occur more when the battery charge is low? Are there any warning lights on the dashboard? With this information, I can better compare it to my experience and suggest whether you might be facing the same underlying issue.

Thanks for sharing your experience. My current mileage is 55720 KM and the last service was done 3 months ago. The spongy brake pedal and inconsistent feedback started happening regardless of the battery charge level. No warning lights on the dashboard yet. The squeaky brakes noise appears mainly during light brake application. The brake fluid was changed during the last service, but the hydraulic brakes still feel unsafe. When pressing the brake pedal, there is a slight delay before the brake system engages, which really concerns me about potential brake rotors issues. I will have it checked at the workshop based on your voltage regulator suggestion. Good to know it might not be a mechanical issue with the brake components themselves.

Based on your latest description of the symptoms, especially the squeaky brakes during light application and the delay in engagement, this sounds different from my voltage regulator issue. While our Smart ForTwo EVs share similar brake systems, these additional symptoms suggest potential mechanical concerns. The squeaking noise during light braking often indicates worn brake pads making contact with the brake rotors. The delay in engagement could mean air in the brake lines, despite the recent fluid change. Since your brake fluid was changed recently, the workshop should check if the system was properly bled. In my case, there was no squeaking or engagement delay, just the spongy feel. Consider having them inspect: Brake pads wear level, Brake rotors for scoring or uneven wear, Proper bleeding of the brake system, Metal brakes caliper movement The repair cost might be higher than my 240€ voltage fix if brake components need replacement. For reference, my brake pads and rotors lasted about 65000 KM before needing replacement, so yours might be approaching end of life. Let us know what the workshop finds. The combination of symptoms suggests this needs checking soon for safety reasons.

Thanks for the detailed analysis. You make a good point about the symptoms being different from your voltage regulator issue. After reading about the typical brake pad lifespan, I checked my service records and noticed my Smart ForFour is actually approaching 60000 KM, not 55720 KM as previously stated. The squeaking during light brake application has gotten worse over the past week. The hydraulic brakes feel increasingly unreliable, especially when the metal brakes components make that concerning noise. Given the symptoms and mileage, I suspect you are right about the brake shoes needing replacement. I scheduled a workshop appointment for next week. Will ask them to thoroughly check the brake fluid system bleeding and inspect the brake rotors condition. The delay in brake engagement is my biggest concern, so better have it fixed properly even if it costs more than your voltage repair. Will update the forum once I get the workshop diagnosis and repair details. Thanks for helping me understand the likely causes, definitely seems more mechanical than electronic in my case.