BMW Repair: overheating, fan clutch, o clock

Question
I have a '96 328ic w/110000 miles. I replaced radiator about 4 weeks ago (pin hole in plastic side). Everything was fine. The other day driving out of town car started to overheat. I pulled over and let cool down, approx 45 min.  I started out to get back home, after about 5-10 miles temp started to go back up to red line.  I stopped again but this time I let it idle, after about 2-3 min. temp gauge returned to normal running temp (12 o'clock pos.) I started out again (55mph)and after 5 miles temp went back up. This continued until I got home, about 45 miles. This was hwy driving. Next day I changed thermostat. When I test drove it did it again. Could this be water pump or fan clutch or something else? I did not let temp get in red zone.

Answer
It is very likely to be the water pump. the impellor can break off the shaft inside. pull the pump out and check. aslo a new t-stat with that is a good idea. the fan clutch is propably OK, if it runs hot when not moving and cools once you move-thats a bad clutch.
          Kimber