water leak 990 sd

I have a bit of a problem with my 08 SD. I'm 800 miles into a 4 thousand mile tour of Europe and my bike is losing water. It's going through about a bottle (250ml) every 250 miles. There's no sludge on the oil cap, I changed the hoses for samco ones at the end of last year and I have checked the tightness of all the clips. There are no drops of water under the bike and it only goes down when hot. The bottom of the airbox is quite wet but I'm not sure where this could have come from. What would you recommend I should check?

So no signs of external leaks? Is the header/overflow overfull with engine hot ie faulty/loose radiator cap?

Cant really help but have a few small suggestions:

no water in oil

tie tissue around hoses joins, run (stationary) until hot and a bit more, turn off then come back when bike cool, check tissue for dampness, often the leaking water evaporates when hot.

could try, running and undo bleed screw, then top up, or drain all coolant and refill as manual states, front lifted, and fill very slowly and bleed

then see what happens, quite often air gets trapped and is a pig to get out

good luck

The water level in the overflow bottle does get higher when engine is hot, I assumed this was normal. I can't see an steam or leaks when running, I would have thought there would have been some residue from that amount of coolant going missing. I'll have a look with the tissue when I get a chance. How much air can get trapped? I must have topped up with about 1 litre of coolant/water so far. I'm having to use water now because I don't have coolant with me. Why would the underside of the air box be wet?

It's wet mostly on the outside left hand side but I suppose it could be coming from the inside. I changed the clamps at the end of last year when I changed the hoses. I didn't raise it up but I would have thought all of the air would have gone by now. Would it show up on the oil cap straight away of would it take a while? Is it likely to cause damage in the next 3k miles if I don't do anything about it and just keep topping up with water?