The clutch system relates to an automatic friction clutch with a hydrostatically actuator-controlled clutch withdrawal. In such clutch release systems, a slave cylinder pressurized by a master cylinder in an engaged state is in connection with a reservoir (tank) via a connection opening uncovered by the master cylinder piston. To determine the opening deviations and location of the connection opening, it is proposed that actuation of master cylinder be velocity-dependent and pressure patterns of the hydrostatic clutch release system be evaluated.