1995 Nissan Altima Problem

I have a 1995 Nissan Altima with over 133,000 miles on it. I was coming home one night and the car started smoking within minutes from my home. I managed to make it to my house in order to put some water in it- I thought it was overheating. When I opened the hood - there was not a lot of smoke nor was there water blubbling up from the radiator. The car just cut off. I took it to the mechanic and he could not find anything wrong with it- he stated he checked everything and everything was fine. Could it be a sensor that burned out and told the car it was overheating? What's wrong with her??? Help???