The contribution deals with the influence of the operating loading on the flow characteristics of the hydraulic pump under laboratory conditions. In the test, a new toothed hydraulic pump and hydraulic oil with kinematic viscosity at 40°C, ν = 64.2 mm2 .s-1 were used. The operational loading was measured during the most difficult agrotechnical operation – ploughing, at which the loading of the hydraulic pump is the greatest. Laboratory testing was determined for 200 hours, and the flow characteristics had been detected at 50 hours intervals. Measurement of the flow characteristics was performed at rated speed n = 1,000 rpm. Measurement of the flow characteristics was carried out in dependence on the loading pressure from p = 0 MPa to p = 20 MPa. When p = 0 MPa, the value reached n = 91.70% and when p = 20 MPa, n = 86.68%. Running-in of the hydraulic pump lasted 150 hours, with an increase of the flow characteristics Δηvol = 1.36% (p = 10 MPa) compared to the initial state. After working for 200 hours, the flow rate of the hydraulic pump decreases compared to 150 hours.