Check condition of the inside of the radiator. If there's alot of calcification in the inside, it can restrict coolant flow enough to create an overheating problem. If there's excessive calcification, then I recommend having the radiator fixed (rodded) by a radiator shop. Rodding entails removing the top and bottom radiator tanks and running a metal rod through the core holes. Afterwards they typically run as good as new.
Don't have the dealer replace it unless you want to pay 2x the cost of a rodding.