BMW Z3 Brake Issues: Weak Pedal & Pump Noise Mystery

Hey! I have some experience working on cars and had a pretty similar issue with my 2003 BMW Z4 last year. When I experienced those symptoms, weak brakes and that annoying pump noise, it turned out the brake system wasn't properly bled after some previous work. Took it to my regular workshop, and they found air bubbles in the brake lines. They did a complete brake system bleed, and it cost me about 90 Euro to fix. The car's been running perfectly since then. Before jumping to conclusions about the brake booster pressure sensor though, could you share: Have you had any recent brake work done? Is the brake fluid level normal? Does the ABS warning light come on? This would help narrow down if you're dealing with the same issue I had.

Thanks for sharing your experience! I'm having the exact same symptoms with my Z3 right now at 48253 KM. I haven't had any recent brake work done, but I did notice the brake fluid level seems a bit lower than usual. No ABS warning light yet, but that persistent pump noise is really starting to worry me. After reading about your experience with the air bubbles, I'm thinking I should get it checked out soon. The weak braking is especially concerning during daily driving. Did you notice any other warning signs before getting it fixed? Really appreciate the help from a fellow BMW owner!

Hey again! Yeah, I totally get your concern with those brake issues, they can be pretty nerve-wracking. Actually, now that you mention the low brake fluid level, that's exactly what I noticed before things got worse with my Z4. The low fluid level combined with those symptoms you're describing sounds really familiar. In my case, before I got it fixed, I also noticed the brake pedal felt a bit spongy sometimes, especially when pressing it repeatedly. The pump noise got more frequent during the last week before I took it in, particularly when I was in stop-and-go traffic. Given your mileage and the symptoms, I'd strongly recommend getting it checked out asap. While my issue was air in the lines, a low fluid level could indicate a small leak somewhere in the system. Better safe than sorry with brakes, right? I learned that lesson the hard way by waiting a bit too long. Keep in mind though, even though our cars are similar, there could be other causes. But based on what you're describing, it's eerily similar to what I experienced. Let me know what you find out when you get it checked. Always good to share these experiences with other BMW owners!

Thanks so much for the detailed follow-up! You've actually got me a bit more worried now about that low brake fluid level. I definitely don't want to end up in a situation where the brakes get worse, especially after hearing about your experience with the spongy brake pedal. I've just called my mechanic and scheduled an appointment for tomorrow morning. You're absolutely right about not taking chances with brakes. Plus, that constant pump noise is really getting on my nerves during my commute. I'll have them check for both air in the lines and any potential leaks, given what you encountered with your Z4. Really appreciate you taking the time to share your experience, it's helped me understand what might be going on with my Z3. I'll update you once I get the diagnosis. Hopefully, it'll be a straightforward fix like yours was. Thanks again for all the help!