I have a 1996 Honda civic ex and it only gets hot when ideling as soon as I take off it goes back to normal. The temp. gauge has not went into the red but it gets close. I have changed the radiator, thermostat, and two new hoses. I have also checked the system with the tube and blue liquid to see if maybe a cracked/blown head gasket test showed all to be good. There is no coolant in oil and no white smoke.

 

welcome to the forum. have you checked to see if the rad fan turns on when it get hot to cool it at idle. fan motor could be out

 

when you changed the radiator did you purge the system of trapped air. if theres an air bubble in the cooling system then the water pump can't properly circulate fluids at idle speeds only when your driving.