Ford Repair: Cooling System, radiator hoses, radiator shops

Question
I have a 1984 Mustang GT-350 20th Anniversary Edition with 2.3L Turbo Engine. I recently had to replace the Water Pump as it was leaking. Since the car is 20 years old, I decided I would replace the Thermostat, Radiator Hoses, Accessable Heater Hoses, Belts and Temperature Sending Switch, even though it only has 30,000 miles. Everthing went well except when I was finshed adding Anti-Freeze I started the car up to check for leaks while at idle sitting inthe driveway. There were none, but much to my surprise, the temperature gauge climbed up to almost HOT before the fan kicked on. This took about 10 minutes or so. After the fan kicked on the temperature barely dropped to the "P" on the gauge. The Thermostate seems to be opening since the upper hose gets hot and I put the Thermostate in the correct way, spring towards the engine, so I'm confussed/concerned. Is this a normal operating temperature condition at idle?  

Answer
Dave-

  First, nice choice on the 2.3L turbo 20th Ann. GT.  I've got my own 20th Ann. 5.0L hatch.  As for the problem, I've had my share of cooling system problems with my car as well.  I would have the radiator checked at a shop that has a good reputation for selling/sercicing radiators (believe it or not there are dedicated radiator shops in many bigger cities).  When mine was tested about 3 years ago (car had about 35K-40K original miles), it was about 70% clogged and wasn't holding pressure very well.  I had similar issues of overheating, especially at idle (and it worsened with the heater on, for some strange reason).  But $140 later I had a new bigger radiator that's worked fine to this day.  Hope this helps.

Steve