I am loosing coolant from my 2005 2.0tdi avant and am trying to determine why.

the car uses the max to min volume over about 150 miles, it doesnt over heat and always runs at normal temp, theres no mayoniase on the inside of the oil filler cap, theres no sign of any oil in the water nor any strange exhaust fumes. Also when i undo the expansion tank cap theres always a little normal pressure there but nothing excessive.

I cant see any leaks anywhere but it could be that the amount leaking isnt sufficient to leave a decent puddle as evidence or I just cant see it!!.

Any one got any ideas as to where to look as a process of elimination as I dont want to assume it the headgasket.

Was even thinking of putting some radweld of similar in but to be honest I dont like that kinda of stuff and would rather have the leak sorted properly.

many thanks guys