WHILE DRIVING IN 10 DEGREE F WEATHER, THE MINI COUNTRYMAN OVERHEATED WITHIN 3 MILES OF DRIVING FROM ORIGINALLY TURNING THE CAR ON (10 MINUTES OF RUN TIME). THE DEALERSHIP NOTED THAT A ROCK PASSED THROUGH THE GRILL THAT PROTECTS THE AUXILLARY COOLING RADIATOR AND DAMAGED THE RADIATOR, CAUSING A LEAK. THE NEW 2021 MINI COUNTRYMAN CARS CONTAIN A ROCK GUARD OVER THE GRILL BECAUSE THEY RECOGNIZE THIS AS A DANGEROUS PROBLEM, BUT THEY HAVE NOT FIXED THE PROBLEM WITH ANY CAR FROM A PREVIOUS YEAR. A SIMPLE ROCK GUARD HAVING BEEN INSTALLED IS A VERY INEXPENSIVE AND CHEAP SOLUTION THAT MINI DOES NOT TELL CUSTOMERS ABOUT UNTIL THEIR CAR OVERHEATS AND THE BILL IS NOT COVERED UNDER WARRANTY. THIS SITUATION WAS DANGEROUS BECAUSE IT LEFT THE VEHICLE OCCUPANTS STRANDED IN FREEZING WEATHER, WHERE ONE PERSON BECAME BORDERLINE HYPOTHERMIC (95F BODY TEMPERATURE).