[malcb]

Use your laser temp gauge/gun to check the temp into and out of the rad on the pipes. At idle you should hardly be needing the radiator fan. You need to know the pump is woring.

PS by "added coolant" you do mean you had straight water and added antifreeze/corrosion inhibitor don't you? Antifreeze/corrosion inhibitor will not make any noticable difference unless you put more than a 35% mix in, that would actually make the rad less effective.