Mini One cooling system issues

Sounds familiar. I had a similar issue with my Cooper a while back. Check the fuse for the cooling grille. A defective fuse could be the culprit, restricting the airflow. Is the grille actively opening and closing? You can usually hear it. What about fault codes, did you scan for any?

Thanks! Where exactly is the fuse located, and how can I tell if the grille is actually working? I haven't scanned for fault codes yet, but I can definitely do that. Any specific codes I should be looking for?

The fuse box is usually under the hood, check your manual for the exact location. As for the grille, with the engine running, you should see it open and close, especially as the engine warms up. If the fuse is blown, it will likely stay shut. Better get the fault codes scanned, if the fuse is indeed blown, it could point to a deeper underlying electrical issue, I'd recommend going to the workshop

Just wanted to give you an update. It was exactly what you described, a defective fuse! Replaced it myself, cost me 52€, and everything seems to be back to normal. Huge thanks for pointing me in the right direction! You saved me a ton of stress and probably a bigger bill at the mechanic.