Help -- Car Overheating At Idle

Hello everyone. I am new to this forum and am very glad to have found it! I hope someone can help me out with an overheating problem. My 98 GP GT with 190K miles has been wanting to overheat when idling (such as sitting in a drive thru or at a red light or in traffic). I only have this problem in the summer when it is hot outside. We have replaced the thermostats and several of the radiator hoses. Also, the radiator and overflow are full and the fan is working properly. There is also a rattling or clicking type noise that can be heard when the engine is at idle.

Someone suggested that the water pump might be going out? We have taken it to two mechanics who said everything "looked okay" to them. (I don't know if they even actually checked anything!)

Any help or suggestions you could give would be very much appreciated as we are out our wits end with this issue! Thanks!!!

I'm a newby too but here is what I would check.

radiator cap
quality of coolant
make sure coolant system is bled of air
check if radiator needs flushing out
make sure thermostat was installed in the correct direction of flow
accuracy of temperature gauge or sensor
operation of electrical fan

How high does the temperature get? Mine was doing the same thing a few months ago with temp getting up to around 220. Finally it started leaking from a bad intake gasket. After repairing that the temps are back down around 200 max.
Make sure both fans are running when it overheats.

Based upon what you said, my 2 cents:

...I changed the water pump on sister in laws 95 GP a year ago 120,000 miles---I compared the old to the new pump. The old pump vanes (blades) had been eaten away by the coolant. This reduced the pump efficiency.

With your mileage, the radiator could be partially clogged. The outside could probably use a cleaning as well.