The invention relates to a valve device for a pressure injection or die-casting machine, said device comprising a body (18) with a valve chamber (21) including a suction chamber and a control chamber, and a sliding valve (20) mounted in the valve chamber, said sliding valve comprising a first portion (34) with a valve head (44) that co-operates with a valve seat (22) on the body in order to open and close the valve and a second portion (35) comprising a piston (38) mounted in the control chamber (21a). The control chamber is connected to fluid control connections (26a, 26b) in order to exert a pressure on the piston (38) so as to control the opening and closing of the valve. The second valve portion and the first valve portion are aligned on the same axis in the direction of movement of the sliding valve and said first and second portions of the sliding valve can be separated from one another and secured to one another using a removable securing member (36, 36′).