So.... the temps are back up in the 90's and I'm starting to see some of the same old temperature regulation issues.
But... it's basically Ok this year. So far. We'll see how it handles temps in the 100's with the AC on.
Still, I figure a recap of things learned recently will help.
1) Idle Air Control Valve has a disproportionate effect on engine temp. No kidding. So I had cause to replace it and if done wrong it'll idle really high, 1300 rpm actually. That drove the temps toward overheat every time. BUT, when I got it calibrated and it idled at 625 this eliminated the temp creep in stop/go traffic and it stays cool at idle. This is the first car I've had that is SO sensitive to idle rpm for heat dissipation.
2) Radiator cap. A good sealing cap that holds pressure makes a big difference. At the age these cats are that cap likely needs renewal.
3) Water Wetter - a detergent additive for coolant. It has stabilized the temp significantly.
4) Wired a switch to the aux fan relay. The aux fan seems to take care of the excess heat when vehicle speeds are low and air temp is high. The thermal sensor doesn't trip early enough for my tastes. I want that engine temp pinned to the N. Wiring the switch was simple. Pin 87 on the fan relay is ground switched and activates the relay. So no modifications to the wiring harness and the original thermal switch is still enabled as well.
I've been over the whole cooling system over the last couple of years and these residual items have made significant improvements each in their own right.