my 94' 940 turbo begins to boil out of the cap vent after driving a few miles even though the temp gauge is at 12:00. I ran the engine at high idle with a thermometer in the expansion tank. the fan didn't come on until it reached 210 degrees, which at that point it started to steam and boil a little, but then quickly cooled down to about 190 within a minute. maybe a bad sensor? a volvo "expert" said it might be the radiator starting to clog slowing down flow. Car has 90,000 miles. also, where is the sensor located for the fan. I found two on the drivers side of the head. jumped the front one and that pinned the gauge, tried jumping the second one, but did not do anything. any thoughts would be helpful. thanks-keith