I will certainly do that once the dust settles.

I drove the car to town today. After burping the system and putting in coolant, it seemed to be running really well. No trouble getting there, then I stopped to drop something off. When I started again it overheated in less than 3/4 of a mile. I called the mechanic I was heading for anyway, and he told me to let it cool for a half hour. I opened the hood and it was so hot I could barely touch the support rod.

After a half hour, it started up again fine, and I drove to the garage, which was perhaps 4 miles away. It would be my luck that his diagnostic tool was acting up, but the code for the check engine light did indicate a cooling problem. He opened the hood to listen to it and we stood there talking about what had been done so far. That's when we could both hear a change in the running sound. He stuck his hand inside the front and found the cooling fan was not working.

I'm not technical enough to explain the entire process but he used a little plug in device that would relay around the fan to see if it was actually functional, and it was. Then he got under the car and what he found, was that the contacts for the fan were corroded and covered in gunk. He said the reason that the acting up was so spotty, was that out on the highway it's a smooth run and continuous working, but when you stop and start like running errands in town, it was more likely to stick and stop working. Then he asked if the AC was working well.

Back in June after the first time it boiled over, I discovered my AC wasn't working and it turned out I needed freon. Both my own mechanic and the one where I took it for that work told me that the AC had nothing to do with the overheating, which was wrong. If the fan is not working right, you're not going to get the cool air in, nor cool air over the engine. And there were times that it seemed not to be putting out enough cold air and I put it down to our unusually hot summer.

Bottom line (for now): He cleaned the contacts off and everything looked good. I was able to drive around town on errands, and then the 25 miles home with no issues. He said it should be fine, but it it happens again, I would likely need a new cooling fan.