Results of probe of the piston hybrid machine combining functions of the pump and the compressor of volume action (pump compressor) are given in article. The studied mashine differs in existence of slot-hole sealing between the bucket and a wall of the cylinder executed in the form of the hydrodiode. The numerical modeling of the movement of an incompressible viscous fluid in the hydrodiode port executed in three-dimensional axisymmetric statement is presented. Effects of turbulence were considered by means of SST model. It is established that the liquid consumption through slot-hole sealing depends on driving direction. The analysis of the physical nature of this phenomenon is made.