Check the thermal clutch on the main fan. Check when engine is hot, ( not running of course ); it should be engaged. I believe that at 105C the aux electric fans would also come on. Best thing to do is get one of those laser piro "point n' shoot" thermometers and check the actual temp of the engine at various points, especially around the temperature sensor which is connected to the VDO gauge.

http://www.maxtool.com/index/Digital_Infrared_Non-Contact_Thermometers.asp

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