I seem to be losing water from my 92 discovery TDI, not a great amount, but I have put in about 3 litres in the the last 2 months. I can't find any signs of the leak anywhere in the engine bay, the heater doesn't appear to be leaking, there doesn't seem to be anything untoward in the header tank and no visible smoke from the exhaust. The car does not overheat, but the temperature gauge does climb a bit higher than normal before the thermostat opens for the first time (probably always has, but i'm constantly watching it now). I am open to any suggestions as to what the problem is.
I also noticed a couple of other things in my hunt for the elusive leak, I would like the groups opinion on.
1) A mystery small bore plastic pipe with a "U" bend on the end, which was laying on the oil filter. I assume this is some kind of breather pipe as I cant see where it could attach to. ( It seems to run from somewhere near the gearbox, but it was too cold to get underneath to check).2) A spare connector on the alternater. I assume that! it is just unused.
Pictures are here
Thanks in advance for any assistance.