OK, yesterday I drove about 200 miles on the turnpike. At speed 70 to 80 miles an hour, with a sustained cruise, the temp needle would creep up. I would turn off the AC, this would help a bit, but eventually I would always end up cracking the heater just a little bit. This would bring scorching air through the vents and displease passengers and driver.

I have been chasing this problem for a while, my Volvo shop pressure tested my system and no leaks, I have a new thermostat and a new 17" electic fan. It is rated to cool up to a 4 liter engine. Fan is always on with ignition, wanted to remove fan thermo from the equation.

My AC is icy, but only until I have to turn it down/off to keep from overheating the engine.

The needle seems to rise more quickly when climbing a hill or with the AC, almost like the engine can't dissipate heat fast enough. My coolant is a beautiful green, and once again, no leaks. System pressurizes (new cap). Could I have a partially plugged radiator, what about the bad head circulation rumors I've heard about. Anyone experienced this before, its driving me crazy.

Any help would be appreciated. Also, I have little problem if ambient temp is below 85 or so. Volvo mechanic couldn't find problem, although it was in the mid 70's all day.

Once again, thanks in advance
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1981 Volvo 244 GL w/ 225K Original B21F and 3spd. auto