Why is my car still overheating?

This car was given to me by my ******, in March 2011 it started blowing freeze plugs and loosing coolant, she got fed up with the car and brought a new one, and said I could have this as long as I got it fixed

June 2011(all freeze plugs and water pump was replaced)-car ran well afterwards

August 2011 notice that I'm loosing coolant from the front of my car. The cause was a cracked radiator. So my mechanic replaced the radiator and I was back on the road.

Sept 2011- on my way home the car overheats all of a sudden like five minutes from my house. I pull over and pop the hood and all the coolant is in the overflow tank and boiling hot out the overflow tank. I call my mechanic and he says to allow the car to cool off for an hour and then get it home and park it. Thermostat is replaced but still overheating so he diagnose it as a blown head gasket

Oct. 2011
after head gasket repair, tune up, and timing chain tensioner replacement car still overheats! I'm Puzzled. Radiator cap was replaced too.