sorry also to be the bearer of bad news, but sounds like a head issue to me also. keep an eye on the temp gauge, shut the blowers off and see if it raises . if it does put blowers on straight away, to lower temp and pull over. if your loosing water out of the header its pressurizing . get it looked at immediately and you may be lucky and save the head.
i had exactly the same thing a fortnight ago,checked combustion on glow plugs and all o.k , also a leak test done on header for combustion gases and all o.k. changed several bits before only the head was left , but turned out to be cracked, new head fitted to rectify problem
hope you have better luck