This paper presents preliminary investigations and experimental results on a hydraulic pump of piston type, driven by a micro-Organic Rankine Cycle. The prototype device is made of two double acting-piston machines as pump and expander and two small heat exchangers working as evaporator and condenser. The working fluid adopted is R134a, which is characterized by suitable properties, in terms of working temperature and pressure values, for the application concerned. The machine is conceived to convert low enthalpy sources, such as hot water generated by solar collectors or biomass boilers, into mechanical power. An innovative aspect of this system is that it presents only mechanical components, without any electronic control system. That makes this machine suitable for several applications, especially in places not reached by electricity supply grid. Generated mechanical power output can be used, for example, to pump water from a suction reservoir to a supply tank or for fields irrigation. A preliminary test campaign, varying the hot water set point temperature in the range 50-75 °C, has been carried out on the prototype device to evaluate the operating parameters ranges of the system in analysis. A description of the test bench set up and of the acquisition system, in house developed in LabVIEW environment, is presented. Preliminary experimental results show that increasing the hot water set point temperature, the ORC maximum pressure increases up to 18 bar. ORC cycle pressure difference between evaporation and condensation side reaches almost 6.5 bar. ORC maximum temperature values increase linearly with hot temperature set point. Pressure head, generated by the hydraulic pump, ranges between 0.6 and 1.8 bar.