overheating 98 mercury sable gs

my 98 mercury sable gs is overheating when im sitting at a red light. it immediately goes back down when i start moving. i flushed the radiator and it did no good. my fans work. the car has 121k miles. do i need a new radiator, a thermostat or what? please help

Check your radiator fan. Start your car and let it IDLE for 15 minutes. Your radiator fan should kick in once or twice by then. If the radiator fan is not turning ON by then, shutdown the engine. Check the radiator fan relay/fuse to make sure they are not bad. You can try to disconnect the electrical connector to the radiator fan and manually supply power to the connector and see if the fan works.

If your radiator fan does work when you idle the car for 15 minutes you may have a dripping water pump. The water pump will leak on the weep hole underneath the water pump itself. It is a sign that the inside seal on the water pump is bad and needs to replace the water pump.

there is a small gap between condensor and radiator that gets leaves,dirt,etc.take plastic cover off bottom car and using high pressure hose spray it out real good.mine was having same problem and i tried everything and turned out to be all it was.