It's possible. Have you ever flushed the cooling system? It may be a good idea to reverse flush the cooling system and replace the thermostat. With winter coming, it is a good idea to do anyway. You also have to remember, the older cooling systems, especially Chrysler and some Fords, were prone to corrosion. I just replaced the rad in my '76 Stallion. The entire back lower seal on the top tank corroded. You wouldn't believe what the inside of the water pump inlet looked like when I also replaced the rad hoses! It's a cheap investment in your Mav. Hopefully, it should take care of the prob. Other than a faulty sending unit on the gauge, I can't think of anything else it could be.