I Have a C200 Kompressor, W203, 2003 Model 271 Engine, What is the black electronic cylinder that fits into the radiator water bottle compartment, as the guys at Mercedes think I'm talking rubbish when i ask for that part, they have no idea what i'm talking about.

Engine coolant temp sensor? http://www.partsgeek.com/gbproducts/WC/6328-01047161.html?utm_content=YN&utm_term=2002-2007+Mercedes+C230+Coolant+Level+Sensor+APA%2FURO+Parts+W0133-1628172+02-07+Mercedes+Coolant+Level+Sensor+2003+2004&fp=pp&gbm=a&utm_source=google&utm_medium=ff&utm_campaign=PartsGeek+Google+Base&gclid=CKGNwv7UwcICFUEV7Aod_DgA3A

Hi Mark Thanks, but this is the switch mounted into water radiator bottle, the unit i am referring to fits in the moulded plastic brackets on the radiator water bottle.

I've checked other vehicles but they do not have this, they do not even have the wire loom connection for this, mine has the wiring which i assume the mechanic has ripped the unit from the loom.

If you check the radiator water bottle, there are two curved moulded brackets that hold this unit, but no one can tell me what it's supposed to hold.

If you check the water tank Pic on parts geek, its the brackets directly below the pressure relief nossle.

If it is the green arrow its your aux. water pump. http://www.pelicanparts.com/techarticles/Mercedes-W203/WATER-Coolant_Expansion_Tank_Replacement/WATER-Coolant_Expansion_Tank_Replacement.htm

Yes, But there are no water pipes connected to this unit, it's entirely black, Cylindrical in shape same size as pic, fits in same position and had an electronic pc board inside, saw this when visiting mechanic one day while he was replacing gearbox, radiator etc.