overheating bad!!! urgent

Hi all I have a 1989 190E it is overheating bad. I have flushed the radiator twice now, replace the thermostat and still overheats, any ideas would be very very helpful, trying to bleed the system of air but does not seem to do anygood can someone explain how to do this properly? help would be very very appriciated thanks, no oil in radiator fluid or water in oil, I am running out of ideas, ohhh and the water pump was recently replaced too.