BMW M4 Overheating Crisis: Fan Failure Warning Signs

I have some experience with BMWs and dealt with a similar issue on my 2019 BMW M2. Really frustrating situation! The symptoms were exactly like yours, overheating warnings and limp mode. Took it to my regular workshop and turns out it was just a faulty wiring connection to the cooling fan. The connector had corroded and wasn't making proper contact. Total repair was 95 Euro, mostly labor costs for diagnosing and fixing the connection. While they were at it, they checked the entire cooling system just to be safe. Before I can share more specific advice, could you share: Any unusual noises from the fan area? Does the problem happen more in traffic or at highway speeds? Have you noticed any coolant leaks? When was your last cooling system service? I'd love to help more once I know these details. The M4 and M2 share quite a bit in terms of cooling system design.

Thanks for sharing your experience! My M4 has 117824 KM and last service was about 2 months ago. I've noticed the fan does make a slight grinding noise when it kicks in, but it's pretty inconsistent. The overheating happens mostly in stop-and-go traffic, but I haven't spotted any coolant leaks under the car. The shop checked all fluid levels during the last service and everything was good then. What you mentioned about the corroded connector sounds promising, might be worth checking that first before diving into more expensive repairs. Did your M2 also take a while to show these symptoms, or did it happen suddenly?

Hey there again! Thanks for those details about your M4. You know, my M2's issues actually developed gradually over a couple of weeks before things got really bad. Started with occasional temperature spikes, then got worse until that dreaded limp mode kicked in. That grinding noise from your fan definitely rings a bell, mine made similar sounds before things went south. In my case, the corroded connector was causing the fan to run at incorrect speeds, which explains the weird noises and inconsistent operation. Since you're experiencing similar symptoms mostly in traffic (just like I did), and given that grinding noise, I'm even more convinced it could be electrical-related. The fact that your fluid levels were good at the last service is another pointer, my coolant levels were fine too when this happened. Here's a tip from my experience, before you take it in, try listening to the fan when you first start the car while it's cold. If it's making that grinding noise right from startup, it's another sign pointing to the electrical connection issue. That's exactly what helped my mechanic diagnose my M2 quickly. Really hope it turns out to be something as straightforward as it was in my case. Keep us posted on what you find out!

Thanks so much for all that detailed info! You've actually made me feel a lot better about this situation. I just went out and did that cold start test you suggested, and sure enough, the grinding noise is there from the beginning. It really does sound like I might be dealing with the same electrical issue you had. I've got an appointment scheduled with my mechanic tomorrow morning, and I'll definitely have them check the fan's electrical connections first. It's such a relief to hear this might not be something major, I was honestly worried I'd be looking at a massive repair bill. I'll update the thread once I get the diagnosis. Really appreciate you taking the time to share your experience in such detail. Having someone who's been through the same thing with a similar car is incredibly helpful. Fingers crossed it's just that connector issue!