Thanks to the responses. Update. The symptoms were as follows:
1) The water temp seemed to run higher this summer than in the past. (I had pulled off the intake over the winter to detail the engine.) With very little "extra cooling" evident on the way home in the evening or night from a cruise.
2) This past Saturday I took a 1/2 hour round trip to get gas and the temperature slowly rose the whole time. By the time I got home the temp was @210 and rising.
3)Checked on Sunday afternoon when it was safe to take the rad cap off. Coolant level was aprox 3-4 in below the opening. Observed bubbles inside as the engine was running.
4) When I ran the engine up in RPM, the fluid level went down to about half.
5) Added some coolant, and as the tempurature approached 180, the fluid started to run out the overflow tube. (I know that water expands as the temp increases) Noticed very little movement of water through the radiator. I have an 180 deg t'stat and expected to see movement at 180 deg. Rad cap was still off. Put the cap on. Rad hoses full and could not squeeze rad hoses.
I found the problem last night
, but will confirm tonight when I put things back together.
Anybody like to take a guess what the problem was?