Started happening to me, as well, even w/the upgraded fan. So I stuck on another 10" fan in front of the radiator. No dice. I think too much heat is getting trapped under the hood. To test my theory, I'm going to remove the hood insert, and drive around on Mon & Tues of next week when the temp is going to be over 100 degrees again. We'll see what she does. I saw another member had ordered a heat extractor and put it on his hood, and it looked pretty good, so I ordered the same one for $95 on eBay. If removal of the hood insert does alleviate the situation, I'll be putting on the heat extractor in short order.
"Bill" from Ron Davis racing also told me this the other day:
If you put a
2nd fan on the front side of the radiator, it blocks airflow and probably only about 30 percent of the airflow makes it through the radiator. Not a good choice.