Normally the radiator is plugged when this happens. Pull the upper hose and look for deposits on top of the circulating fins. A water pump impeller can rust of but this normally happens if your running without anti freeze. I assume your fan is turning on if not use a small hammer and tap the motor if it starts buy a new fan motor. You can use a DVOM and check for power to the motor just make sure you also have a ground. You can also swap the air conditioning and normal relay. The temperator sensor for the computer should turn on the fan. Install a 192 degree or 195 degree thermostat or the computer won't work properly dropping gas mileage.