Apparently, my problems are not over! Replaced the radiator cap and put in a new thermostat. Flushed system and added coolant at 50/50. Took a 15-mile highway run and the gauge got to the 5/8 mark while cruising at 65-70. Cooled down to 1/4-3/8 when I got off the highway and was making my way through traffic lights.
I wouldn't want to drive this thing a long way until I have a better understanding of what is going on. I do think I had a bad rad cap, but I also think it wasn't causing any problems until a few days ago when it overheated for the first time. What I don't know is why is it now running hot? And variable temperature--used to be the temp gauge was always rock steady at 1/8-1/4.
If my water pump was going, wouldn't you expect the temp to go down at highway speeds and get hotter in stop-and-go traffic? I seem to have the opposite problem.
