http://catalog.worldpac.com/mercedesshop/sophio/image.jsp?title=Water%20Temp.%20Sensor&url=http%3A//img.eautopartscatalog.com/live/C602012373FEB.JPG
In the water jacket ..I think in the head on that chassis..you will find it
Continuous Injection System
The sensor is 2 thermistors in one case , so they have to read the same , regardless of temp... the ohm reading is taken diag across the pins for each sensor..