GregFord

Thanks Pete. So it's an anti-icing function, to stop crankcase fumes freezing and blocking the breather as they drop pressure at the valve. Very interesting. The temperature here in Catalunya very, very, very rarely drops below 8C. But anyway, it is as it is. I have another question (entirely different problem) but I'll start a new thread. Thanks again.

Found it - on Amazon of all places. Still not sure exactly what it does but at least I can now order a new one and fit it. The part number is: 036 121 188 B

A leak started two days ago behind the engine. Couldn't see where it was coming from. Pulled the media player out, put in the engine bay, connected the reversing camera and managed to view the leak realtime. Has to buy a spline set to take the inlet manifold off. With the manifold loosened I could see that there is a chamber that plugs into the inlet manifold an that also has the water passing through it on route to the resevoir. Took the chamber off and tried to seal it. Nearly worked but not quite. So I need to order one. Trouble is I have no idea what it's called (or what it does exactly) and I was unable to find a part number anywhere on the part itself. This is the part in question, that's leaking, but what is it called so that I can order new one?