Originally Posted by Ethan

Cunix is refering to what I call freeze (core) plugs, and they can leak on some cars.

The theory of the t-stat is when car is cold and started up coolant only circulates throught the engine block. Once a temp sensor or t-stat detects enough heat the car starts to circulate coolant thorugh the radiator to be cooled by the air rushing through the radiator fins when the car is moving.

So when you start up car when cold the top hose should stay cool for a period then get hot. An infra -red thermometer is a good tool for taking temp readings of the radiator to see if it gets a rush of warm coolant from the t-stat opening.

If your driving and your temp gauge (working) reads as normal then your t-stat, radiator core and (hoses -are not collapsed) and are in good shape.

For leaking check out water pump seals, cracks in hoses, heater matrix all things that will leak when engine gets warm and you'll get either odor or drips.

Alos C-class cars have some heater hoses and components not found on other makes so be sure any garage you go to KNOWS Mercedes.