BMW i4 Brake Booster Sensor Issues: Warning Signs & Fix

Had a similar issue with my 2019 BMW iX3. Started with inconsistent brake pedal feel and warning lights. Turned out the brake system was incorrectly bled during routine maintenance. The mechanic had to completely drain and properly rebleed the system. The symptoms matched yours, noisy hydraulic pump and strange brake response. It was serious enough that I wouldn't recommend driving much until fixed, as it affects brake performance. The repair involved checking the brake booster, pressure sensor, and ensuring no air was trapped in the lines. My advice: Have them specifically check if there's air in the system first. Ask them to verify the brake fluid level and test the pressure sensor before replacing parts. Also request they document the brake fluid pressure readings before and after the service. Hope this helps with your i4 situation.

Hey, thanks for sharing your experience! That's really helpful since I'm dealing with the exact same symptoms. I ended up getting it looked at and they also found air in the brake lines on my i4. Quick question, do you remember roughly how much you paid for the complete service? Also, has everything been running smoothly since the repair, or have you noticed any other issues pop up? Would love to know what to expect in the long run.

Hey there! Just wanted to follow up about my iX3 brake repair. After getting it fixed, it cost me 90 € for the complete service, not too bad considering how important brakes are! The mechanic found and fixed the brake booster pressure sensor that was acting up, plus they properly bled the brake system to get rid of all that trapped air. I'm happy to report everything's been running perfectly since then, no more weird noises from the hydraulic pump, and the brake pedal feels normal again. It's been several months now, and I haven't had a single issue pop up. The brakes respond exactly like they should, and those annoying warning lights haven't come back either. Looking back, it was definitely worth getting it sorted right away. These electric BMWs are pretty solid once you get the brake system properly set up. Just make sure to keep an eye on your brake fluid levels during regular maintenance, and you should be good to go!

Thanks so much for following up! Just got back from the mechanic today, and you're spot on about getting it fixed quickly. The whole ordeal ended up costing me a bit more, around 120 €, but totally worth it for peace of mind. They found the same issues you mentioned, and even showed me where the air was trapped in the system. Funny story actually, while I was waiting at the shop, I got chatting with another BMW owner who had the exact same problem. The mechanic was super thorough, took the time to explain everything, and even gave me some tips for preventive maintenance. Such a different experience from my last mechanic! The car's driving like new now, no more weird noises or warning lights. The brake pedal feels solid again, and that annoying hydraulic pump sound is gone. Really glad I didn't put this repair off any longer. Thanks again for your help in figuring this out!