BMW X4 Coolant Leak & Overheating: Help Needed

Hey there! I've got some experience working on BMWs. I had a similar issue with my 2019 BMW X3 last year. I know the frustration you're going through. When my car started showing those exact symptoms, overheating, limp mode, coolant warnings, turned out it was a faulty connection in the wiring harness to the coolant control module. The plug had corroded and wasn't making proper contact. My mechanic found it pretty quickly, replaced the wiring connector and cleaned up the connection points. Cost me 95 Euro and solved all those issues completely. But before jumping to conclusions, could you share: Are you losing coolant quickly? Does it happen more when the engine is hot or cold? Any unusual noises from the engine bay? The X3/X4 models can be tricky with cooling system electronics, but knowing these details would help narrow down if you're dealing with the same issue I had.

Hey, thanks for the detailed response! I have the same issue right now at 154444 KM. I'm losing coolant pretty fast, I'd say about a quarter of the reservoir every couple of days. It mostly happens when the engine's hot, usually after about 15-20 minutes of driving. No weird noises that I can hear, though. Just had it serviced last month and everything was fine then. Your electrical connection theory sounds promising, I'll definitely have my mechanic check that. Really hoping it's just a wiring issue like yours and not something more serious with the cooling system itself. These electronics can be such a pain sometimes! Let me know if you think of anything else I should look out for. Really appreciate the help!

Hey again! Thanks for those extra details about your X4. that coolant loss rate sounds really familiar, my X3 was drinking coolant at almost the exact same rate before I got it fixed. After hearing about your coolant loss pattern, I'm actually starting to think it might be something different from what I initially suggested. While the wiring harness fixed my first round of issues, I actually had a second episode a few months later with similar symptoms. Turned out the electronic water pump was failing, it wasn't running at the right speed when the engine got hot. The symptoms were pretty much identical to what you're describing. The pump failure typically shows up around 150,000 KM, which matches your mileage perfectly. On these newer BMWs, the electric water pump can get weird before completely failing, running too slow, too fast, or intermittently. That would explain the overheating when hot and the coolant loss. My mechanic replaced the water pump assembly (ended up being pricier than the wiring fix, unfortunately), but it's been running perfectly for the last year. Might be worth having them check both the wiring and the pump while they're at it. Just wanted to share this since your symptoms are matching my second experience so closely. Let me know what you find out when you get it checked!

Thanks for sharing that additional insight about the water pump, that actually makes a lot of sense! The timing with the mileage is spot on, and it would explain why it's getting worse when the engine's hot. I've booked it in with my mechanic for tomorrow morning. I'll have them check both the wiring harness and the water pump. Even though the pump replacement might cost more, I'd rather fix the real issue now than keep losing coolant and risking more damage. Really grateful for your help and sharing your experiences, it's given me a much better idea of what to expect when I take it in. I'll update you once I know what the actual problem is. These BMWs are amazing when they're running right, but when something goes wrong, it's like solving a puzzle! Thanks again for taking the time to help me out with this!