New 2020 Sprinter. I'm not familiar with the engine (yet), but at 4400 miles (picked up at 4000 from Winnebago dealer). The fan assembly, which appears to be threaded on to one of the pulleys, has "spun off" and is simply flopping around inside the shroud. I'm having it towed next week to the one and only local MB dealer, but what on earth can cause this to happen? I heard intermittent clattering on a short drive, parked in my driveway, and discovered the issue. Fortunately, this did not happen on the 400 mile drive from the RV dealer. I'd assume the normal rotation of this pulley would tighten the threads! Anyone else experienced this?