240 overheating

I just arrived home from buying a 240 in San Francisco. As I was driving across the Arizona Death Valley I noticed that as I went up hills or mountains that the temp. gauge went almost to red zone, almost every time.. Any advise would be helpful, ma says that the temp. sensor is probably in the front of the engine and that when the car was leaning back on the hills that the sensor was more likely to read hot... Please help. Joseph