[HIZNHRZ]

Yun, with time and mileage (depnding on driving conditions) the conditions you are describing are what I experienced with my Red/Gray 91 fair weather daily driver. At the time the car was about 10 years old and had ~15K (very short commute to work) miles. I pulled the radiator and cleaned it and the car again ran cool again. If you saw what I cleaned out of the radiator fins you would have thought I drove the car at the beach. It was a very fine sand like material. It was almost more like dust than sand but the radiator was packed with it; especially towards the bottom. After cleaning it out, it was only about another year before the running unusaully hot conditions returned.

I pull the radiator again. Mileage was only another ~8K miles but the radiator was as loaded with sand/dust like material again that was very hard to see when crawling under the car or when looking from the top. This time I replaced the radiator with a Fluidyne radiator and thermostat. The car ran cooler than it ever had. It's only a guess but I'm thinking the stuff that loads up the radiator has something to do with the crap thrown on the streets in the winter.

I sold the car soon after. I do talk to the new owner. The car now has over 30K miles and the new owner has never brought up and cooling issues. The only other thing I can say is the stuff was very hard to clean out. I'm thinking as the open area aperture becomes restricted and it not only impedes air flow and cooling but it also loads back up again much quicker. I don't think it's your problem but I also have a 160 degree thermostate you are welcome to if you wanted to try it.