yesterday I removed the Air filter housing because supposedly the aux water pump was placed beneath it. Well it isn't. There was nothing ther but a solid pipe. There is however a switching unit in the area of the battery. It looks like three cylinders on a plate. Two low ones and a higher one. (I'll make a picture and post it). I assume this is the aux pump. It is out in the open so easy yo test and replace. The clicking and the play in the pump dissapeared after running and shutting down the engine (????).
I agree that I am most probably looking at a head gasket that has seen better days. I'll consider taking the car to the Benz dealer and have them pressure test the system. I can not see any coolant laeking anywhere and as far as I can see the waterpump is dry all around. It is near freezing point ambient temperature here and even after heating up the engine there is pretty much white vapor coming out of the exhaust, but then I see so many cars do this in this weather so I am not certain that this is a tell tale sign of a broken gasket. I guess that just guessing will not provide with the answers I need so I will have to invest in a real test.
Wish me luck,