Translation:The hail did some damage to my new car.
Ma nouvelle voiture means my car that is new to me. It may not be a brand-new car but I haven't had it in my possession long. It is subjective.
Ma voiture neuve means my brand-new car. This car is new from the dealership. "The latest model." In this case it is objective and follows the noun.
if I have understood correctly your explanation I translate in french an example
la grêle a fait ( a causé ) des dommages sur ( à ) ma voiture neuve = the hail did some damages to my new car
la grêle a endommagé my voiture neuve = the hail has damaged my new car
isn't it ?