Engine Over Heat At Idle

[DOBOY1988]

My Pony has 2.3L, is a 4 banger, 1988 LX Mustang Conv't. Got it from a neighbor who cheated me badly (the odometer was set back 100K, actually 157K). After some major repairs, I managed to restore the car for fun drives in summer.

It is a fuel efficient car (21 - 25 mpg) , compared to its bigger-engined brother 5.0L. However, I find it bothering recently that if I let the engine idle running, the temperature gauge would rise and rise and eventually kick in the cooling fan. Even in cold Chicago winter weather here; unbelieveable!

I have so far, replaced the fan relay module, which was burnt out outside the Cominski Park last summer due to overheated wiring, flushed the coolant, replaced the water pump, and the thermostat. But the symptom seemed to reduce just a bit. Is it true that this 2.3L engine was designed to get hot at Idle? The cooling fan kicks in often in summer time if I don't use the air conditioning, or the heater when I got caught in still traffic.

This pony runs fine when it is moving, just that it doesn't like to sit in traffic, I can't figure out why.... One thing I suspect though, I have done some body work (3) years ago, and may have painted the radiator fins in the front, I wonder if I straight out the fins and remove the painted stains, could I get a better result?

If anyone have ever had experience like this, I would like to learn a few tricks to correct this problem.

Many thanks in advance!

DOBOY1988