Monitoring method of a hydraulic circuit of a work vehicle, the vehicle including - a hydraulic circuit operatively connected to a fixed displacement hydraulic pump and a prime mover arranged to drive the hydraulic pump in rotation, - a hydraulic actuator arranged to be powered by the hydraulic circuit through an open center directional solenoid valve, wherein the actuator includes a movable shaft, and - a control lever (JOYSTICK) arranged to control an opening of the directional solenoid valve, the lever comprising a release position corresponding to a zero opening position of the directional solenoid valve in which the entire pump flow is sent to a hydraulic tank, and a position of maximum deviation corresponding to a position of maximum opening of the directional solenoid valve in which all the flow generated by the hydraulic pump is sent to the hydraulic actuator, the method including the following steps: - (a) Monitoring of a position of a movable spool of the directional solenoid valve, when it is detected that the movable spool is in the condition of maximum opening, then - (b) Acquisition of two positions (X1, X2) of the movable shaft in two distinct instants identifying a predetermined time interval, - (c) Calculation of an effective flow rate (Qr) of the hydraulic pump as a value proportional to a ratio of a distance between said two positions (Dist (X1, X2)) and said time interval, - (d) Calculation of a nominal flow rate (Qn) of the hydraulic pump as the product of a value of the displacement of the hydraulic pump for an average value of the rotation speed of the hydraulic pump in the time interval and (e) Calculation of an efficiency (η) of the hydraulic pump as a ratio between the effective flow rate and the nominal flow rate. - a hydraulic circuit operatively connected to a fixed displacement hydraulic pump and a prime mover arranged to drive the hydraulic pump in rotation, - a hydraulic actuator arranged to be powered by the hydraulic circuit through an open center directional solenoid valve, wherein the actuator includes a movable shaft, and - a control lever (JOYSTICK) arranged to control an opening of the directional solenoid valve, the lever comprising a release position corresponding to a zero opening position of the directional solenoid valve in which the entire pump flow is sent to a hydraulic tank, and a position of maximum deviation corresponding to a position of maximum opening of the directional solenoid valve in which all the flow generated by the hydraulic pump is sent to the hydraulic actuator, the method including the following steps: - (a) Monitoring of a position of a movable spool of the directional solenoid valve, when it is detected that the movable spool is in the condition of maximum opening, then - (b) Acquisition of two positions (X1, X2) of the movable shaft in two distinct instants identifying a predetermined time interval, - (c) Calculation of an effective flow rate (Qr) of the hydraulic pump as a value proportional to a ratio of a distance between said two positions (Dist (X1, X2)) and said time interval, - (d) Calculation of a nominal flow rate (Qn) of the hydraulic pump as the product of a value of the displacement of the hydraulic pump for an average value of the rotation speed of the hydraulic pump in the time interval and (e) Calculation of an efficiency (η) of the hydraulic pump as a ratio between the effective flow rate and the nominal flow rate. - (a) Monitoring of a position of a movable spool of the directional solenoid valve, when it is detected that the movable spool is in the condition of maximum opening, then - (b) Acquisition of two positions (X1, X2) of the movable shaft in two distinct instants identifying a predetermined time interval, - (c) Calculation of an effective flow rate (Qr) of the hydraulic pump as a value proportional to a ratio of a distance between said two positions (Dist (X1, X2)) and said time interval, - (d) Calculation of a nominal flow rate (Qn) of the hydraulic pump as the product of a value of the displacement of the hydraulic pump for an average value of the rotation speed of the hydraulic pump in the time interval and (e) Calculation of an efficiency (η) of the hydraulic pump as a ratio between the effective flow rate and the nominal flow rate.