BMW 3 Series: Brake System Warning & Pump Noise Issues

Hey there! I've got some experience working on cars and had a really similar issue with my 1998 BMW 5 Series. Those symptoms sound exactly like what I dealt with last month! My brake system was giving me the same trouble, warning light, weak braking, and that annoying pump noise. Took it to my regular workshop and it turned out they needed to properly bleed the brake system. Apparently, there was air trapped in there causing all these symptoms. The fix cost me about 90 Euro and solved everything. Before you jump to conclusions about the pressure sensor, I'd really need to know: Have you noticed any brake fluid leaks? When did these symptoms first start? Have you had any recent brake work done? Let me know these details and I can share more specific advice based on my experience with both my 5 Series and my current 3 Series.

Thanks for the input! My car's actually due for service soon (last one was at 78360 KM), and I haven't noticed any fluid leaks. The symptoms started about two weeks ago, pretty suddenly actually. Haven't had any brake work done in the past year. The bleeding suggestion makes a lot of sense, might explain why the pump's working overtime. I'll definitely get that checked. I was worried it might be something more serious (and expensive!), so this is somewhat relieving to hear. Did your pump also run more frequently before you got it fixed?

Hey again! Yes, absolutely, my pump was cycling way more frequently than normal before I got it fixed. It's exactly what you're describing. When I first noticed it on my BMW, I kept hearing the pump kick in even during normal driving, which definitely wasn't normal. Since you mentioned it started suddenly and you haven't had any recent brake work, it really does sound identical to what I experienced. In my case, the trapped air was making the pump work extra hard to maintain proper brake pressure. That's why it was cycling so often and making those weird noises. Just to give you a heads up based on my experience, when they bled my system, they also found that one of the bleeder valves was slightly corroded, which might have contributed to the air getting trapped in the first place. Might be worth having them check yours too while they're at it. The fact that you haven't noticed any fluid leaks is actually good news. When I was freaking out about my brake issues, I was worried about sensor failure too, but honestly, a proper bleeding solved everything. The warning light went away, braking feel returned to normal, and most importantly, that annoying pump finally stopped its constant cycling. Let me know how it goes after your service appointment! Since your car's about the same age as mine was when this happened, I bet you'll have similar results.

Thanks so much for all the detailed info! I've gone ahead and booked my car in for service next week, actually moved it up because I don't want to risk any brake issues. Really hoping it's just the bleeding that needs doing, especially after hearing about your experience. What a relief it might not be the sensor! You mentioning the corroded bleeder valve was super helpful too, I'll definitely ask them to check that while they're at it. Would hate to have this problem come back because of a worn valve. It's crazy how similar our issues sound, right down to the pump cycling and those warning lights. I'll update you once I get it sorted. Thanks again for taking the time to share your experience, it's made me feel way better about the whole situation. At least now I won't be going in blind when I talk to the mechanic!