E39 overheating

Crazy88 · 2009-08-28T21:57:18+00:00

Hello,Two nights ago I was driving along and looked down and notice the temp guage was in the red. Pulled over immediately and waited for it to cool down. Started it up and drove for about two miles, everything was normal and then it heated up again. Had to pull over and let her cool down a few times before getting home.Next day drove to work. Worked fine for about 5 miles, then heated up again. Did not go into the red, however it constantly went up and down.Took it to the local mechanic today. He told me it was the fan clutch. He replaced the fan clutch. Drove it home today, half way there you guessed it....temp was heating up. It did NOT go into the red. It got to about the one o'clock position. Temp went up and down constantly.Got to my driveway. Temp was running hotter than normal but did not go into the red while the car was idling in the driveway.Here is whats interesting!! I turned on the heat, and moved the vent control to the heat position. The temp immediately went down to normal!Then as an experiment I turned the AC on and moved the vent to the cold position. The temp guage started going up. Then I turned on the heat again and moved the vent to the hot position, then temp went down!HELP! What could it be?Yes the radiator has plenty of coolant. Do you think it's the thermostat?