As far from JBS as possible !
If your only loosing water when driving and there is no white smoke loosen the water reservoir cap so there is no pressure build up in the system. If the car stops loosing water it`s because there is a pressure build up in the system forcing the water out of the expansion over flow pipe. If the head has already had K Seal in it then that might have stopped the leak but blocked one or several engine coolant channels ( engine would probably run hot if used for a long journey or driven hard ) or the hole is small enough not to let enough water through when turned off but when the pressure ( which is very high ) is built up in the head that is enough to blow the water back out the system. Just an idea as seen both thing happen before. If either of the above your in the screwed and need a new head.
06 Audi 2.0 PD140 Sport TDI Quattro S-LINE.
Old engine 330 bhp @ flywheel 263 bhp @ wheel 490 lb torque.
Audidriver write up HERE
Now stripped and playing with an uprated Cryo treated engine fitted with bigger turbo,water/methanol,uprated injectors etc etc.Wanting 400 bhp and 500 lb torque.
Other car 500+ bhp MK4 Golf R32 turbo