I wouldn't think this can happen. While going through some light duty mowing, the engine compartment all of a sudden went really quiet but it was still running. Short while later, overheating began. I stopped it right away and was able to save the engine. It turned out that the fan assembly came off the pulley and the belt was just sitting there. I looked at it closer and it looks like the shaft actually sheared off (judged by what I saw where it broke off) leaving its end still inside the mounting hole. Has anyone seen this before? Do you have any suggestion on what to do next besides calling the dealer?