1999 Mitsubishi Galant Overheating

About a year and a half to two years ago, I began experiencing intermittent heating issues with my galant. All of a suddent the gauge would spike, but then the fan would kick on and it would drop. I had the thermostat replaced and that seemed to do. It started up again. Less then a year after that it started doing the same thing again. I took it to my mechanic who flushed the system adn it was fine for about a year. About a month or so ago, it started doing it again, so I had the coolant flushed again and everything seemed ok. Now, just today the temperature gauge shot up while I was driving to work. I blasted the heat, but the temp gauge hovered closed to the red pretty much the entire time. Any ideas? Replace radiator, replace water pump, clearly a coolant flush won't last for long. Thanks to whoever answers this.