BMW X4 Brake System Nightmare: Pump Issues & Error Codes

Hey there! I had a somewhat similar issue with my 2020 BMW X3 last year. I've got some experience working on cars, but nothing too advanced. My symptoms were pretty close to what you're describing, weird brake behavior and that annoying pump noise. Took it to my regular workshop, and it turned out the brake system wasn't bled properly during a previous service. They had to do a complete brake fluid flush and proper bleeding. Cost me around 90 Euro to fix, and all those issues disappeared. But before jumping to conclusions, could you share more details about when these symptoms started? Did this happen after any recent brake work or maintenance? Also, what specific error codes are you getting? This info would help figure out if you're dealing with the same problem I had or something else. BTW, if you want another opinion, might be worth checking the X6 forums too, they share a lot of similar brake components with the X4.

Thanks for the detailed response! My X4 just hit 57663 KM and had its latest service about 2 months ago. The issues actually started right after a routine brake pad replacement. I'm getting the "Drive moderately" and "Brake system malfunction" warnings on the dash. What's interesting is that the symptoms seem worse during cold starts, and the pump noise becomes more noticeable after driving for a while. Your bleeding issue theory makes sense, I'll definitely get that checked out. Did your pump also make that whirring sound even during light brake pedal pressure? Just trying to confirm if we're experiencing the same symptoms before I head to the workshop.

Hey again! Yes, that really sounds familiar, especially the part about it starting after brake work. My X3 was making that exact same whirring sound with even the lightest touch on the brake pedal. Super annoying, right? Looking at what you're describing, I'm now even more convinced it's the same bleeding issue I had. The cold start symptoms are particularly telling, that's exactly what I experienced. The air in the system tends to be more problematic when the fluid is cold, which explains why it's worse during those first few minutes. Just to add to my previous response, when I had the work done, the mechanic showed me how tiny air bubbles in the system were causing all this drama. The brake fluid wasn't just improperly bled, but had also absorbed some moisture over time, making things worse. Since you mentioned it started after a pad replacement, I'd bet good money that's when air got into your system. My advice would be to get it checked out sooner rather than later. While it was a relatively simple fix in my case, driving around with partially compromised brakes isn't something you want to mess with. Let me know how it goes, really curious if it turns out to be the same issue. The symptoms are just too similar to ignore!

Thanks for all your help! You've definitely given me more confidence about what might be wrong. I just booked my X4 in for tomorrow morning, specifically mentioned the bleeding issue and they seemed to agree it's likely the culprit. The symptoms matching your experience, especially that annoying whirring sound and the cold start issues, makes so much sense now. I was worried it might be something major like the brake booster pressure sensor, but this sounds way more reasonable considering it started right after the pad replacement. I'll make sure they do a complete brake fluid flush and proper bleeding. Fingers crossed it's as straightforward as your repair was! Really appreciate you taking the time to share your experience, it's helped me avoid potentially expensive diagnostic tests for other issues. I'll update this thread once I get it sorted, might help someone else with similar problems down the line. Thanks again for walking me through your repair journey!