Problem with cooling water

So the problem is this. My father’s S60 2,4d (130hp) already showed for the second time in the on-board computer “put off the low-engine water” (that’s how it was in it). The first time was a year ago 2008 and the second one was jetz, so a few weeks ago. I was at Volvo dealer and he filled up the cooling water and checked the hoses. Has it checked with the pressure and found nothing. Everything is dry, both in the garage and in the engine room. the year must be felt?