[TR] TR6 overheating puzzle

[Tim Gaines]

I need ideas.  My 1974 TR6 has always run pretty cool, until recently.  Now, whether moving or not, the temp gauge goes to about 3/4 or a little above.  There is no sign of white smoke at startup or cruising, and there is no milkiness in the oil.  The engine runs smoothly, idles normally, and accelerates normally.  Here is a list of what I've done, each time checking for improvement with a drive.  No luck.

1. Checked the thermostat in water on the stove.  It opens at about 160 degrees.
2. Tightened the drive belt (it was a bit loose).
3. Flushed the system with radiator disconnected after removing the drain plug on the engine and poking through the sludge.  Water drained clean when I ran it into the thermostat opening, drain plug area, heater hose, and both radiator hoses.
4. Ran water through the radiator both ways and it seemed to move quickly and was clean.
5. Braced the air cowling which had sagged a bit in front of the radiator.
6. Put on a new thermostat.
7. Removed the water pump (3 years old).  It looks clean and turns smoothly.
8. Flushed the system again.  Water ran clean out of the pump opening before I replaced the pump (with new gasket).
8. Replaced the radiator with a new one.  I was desperate to make a fairly long drive Friday, but that now seems out of the question.  This buy really hurts!

I'm now at a loss.  Can you give me an idea for something else to check?

Thanks,

Tim Gaines
Clinton, SC