BMW i5 Brake Warning: Pump Noise & Weak Braking Issues

Hey there! I had a similar issue with my 2022 BMW i4 last year (I also own an iX). I've got some experience working on cars, though I mostly leave the complex stuff to professionals. The symptoms you're describing sound exactly like what I dealt with. Turned out the brake system wasn't properly bled after some routine maintenance. The workshop found air in the lines, which was causing that weak brake feel and the warning light. Got it fixed for 90 Euro, they did a complete brake system bleed and everything went back to normal. Before jumping to conclusions about the sensor though, could you share: Does the pedal feel spongy? When did you last have any brake work done? Does the noise happen only when you press the brake pedal? This info would help narrow things down better.

Thanks for the detailed response! Just had my service at 173977 KM and yeah, the pedal definitely feels spongy. The noise actually happens even when I'm not touching the brake pedal, it's this constant humming from the front, and it's getting more noticeable. No brake work since I got the car, but this issue started about two weeks after my regular maintenance. Your bleeding theory makes a lot of sense, especially since the timing lines up with my recent service. Guess I should take it back to have them check if they properly bled the system after the maintenance work. Thanks for sharing your experience, it's super helpful to know this was fixable without any major repairs in your case.

Thanks for the follow-up! Yeah, that timing after your service is definitely a red flag. You've pretty much confirmed my initial suspicion, sounds exactly like my situation. That constant humming you mentioned is what really caught my attention because that's precisely what my i4 was doing. The pump was working overtime trying to build up pressure in a system that had air bubbles. Quick tip from my experience, when you take it back, make sure they do a complete system bleed, not just a quick one. My first visit they did a quick bleed and the problem came back after a few days. Had to go back and have them do it properly. The funny thing is, I actually thought my brake booster sensor was shot too at first (like you initially suspected), but it turned out to be such a simple fix. These new BMW brake systems are pretty sensitive to air in the lines, even a tiny bubble can cause all these symptoms. Since you're still under service warranty and this started right after maintenance, they should sort this out for free. Don't let them try to charge you for fixing their oversight. Let me know how it goes, I'm curious if it's the same issue I had!

Really appreciate you taking the time to share all this detail! That's such a relief to hear about your similar experience and how it was resolved. You're absolutely right about getting them to do a complete system bleed, I'll definitely insist on that when I take it back tomorrow. The fact that you had the same humming sound really confirms it for me. I was getting worried about potential expensive repairs, but this makes total sense given the timing after my service. I'll make sure to mention that I know it started right after the maintenance and should be covered under warranty. Actually feeling much better about this whole situation now, it's great to know it's likely just trapped air rather than a serious component failure. Will probably save me a bunch of money and stress! Thanks again for all the helpful advice and for sharing your experience. I'll update you once I get it sorted!