BMW 8 Radiator Fan Failure, Overheating Issues & Fix

Hey there! I've got some experience working on BMWs, nothing too fancy, but I've dealt with cooling issues before. Had a similar problem with my 2020 BMW 7 diesel (switched from that to a 5 series later). The symptoms were exactly like yours, fan not working, engine temp rising, warning lights. Turned out it was a speed sensor that was completely shot. Got it fixed at my regular workshop for about 250 Euro, and that sorted everything out. Just to help you better, could you share: Current mileage? Any unusual noises from the fan area? When did you first notice the problem? This could help narrow down if you're dealing with the same issue I had. Best to get it checked soon though, these cooling problems can get nasty if left unchecked.

Thanks for the detailed response! My current mileage is 42168 KM, and I just had my routine service last month. Haven't noticed any weird noises from the fan area, it's just completely silent even when it should be running. The problem started about a week ago, first noticed it during a longer drive when the temp gauge started creeping up. Based on what you're saying about the speed sensor, that could definitely be it. Did you notice if your fan stayed completely dead like mine, or did it try to work occasionally? Will get it checked out ASAP, don't want to risk any engine damage.

Hey again! Thanks for those details. Yeah, this really sounds similar to what I experienced with my BMW. In my case, the fan was completely dead too, not even a slight attempt to spin, just like yours. When I had the sensor issue, it was also right after a service, around the 45000 KM mark. The timing of your problem starting during a longer drive is also very familiar, that's exactly how mine acted up. The temperature would creep up slowly, especially when idling or in slow traffic. Just to share my full experience, I initially thought it was just the fan itself, but my mechanic checked the entire cooling system and found that dead speed sensor. The sensor wasn't sending the right signals to the fan control module, so the fan wasn't getting the command to kick in at all. Quick tip though, while you're waiting to get it checked, try to avoid sitting in idle for too long and maybe keep the climate control off to reduce the heat load. That's what I did to safely get to the workshop. The good news is that if it is the sensor, it's a relatively straightforward fix. Definitely way better than having to replace the entire fan assembly, which is what I was worried about at first!

Thanks so much for all the helpful info! That's really good to know about the sensor being the likely culprit, definitely puts my mind at ease a bit knowing it might not be the entire fan assembly. I'll follow your advice about avoiding idling and keeping the climate control off until I can get it to the shop. I've actually just booked it in for tomorrow morning. Called my regular mechanic and mentioned the speed sensor possibility, he seemed to think that made a lot of sense given the symptoms. Really hoping it'll be a quick fix like yours was! Will probably cost a bit, but better than risking more serious engine problems. Thanks again for taking the time to share your experience. Really helped me understand what might be going on with my car!