Abstract: The present invention relates to a method for starting a fuel cell stack at temperatures below the freezing point of a reaction product produced during the reaction between an anode-side fuel and a cathode-side fuel. The fuel cell stack comprises a plurality of individual cells having at least one internal cell which is arranged in the stacking direction in the interior of the fuel cell stack and an edge cell which is arranged in the stacking direction at the edge of the fuel cell stack. The fuel cell stack is connected to a cooling circuit having cooling fluid for cooling the fuel cell stack, which cooling fluid can be conducted through the fuel cell stack by a pump arranged in the cooling circuit.

Abstract: A method is for testing a hydraulic system (1), having a pump (2) which, in a first direction of rotation (3), conveys fluid to a first consumer (4) for a volume flow function and, in a second direction of rotation (5), conveys fluid to at least one second consumer (6) for an actuation function. The method includes testing hydraulic readiness of the hydraulic system (1); drawing fluid into the hydraulic system (1); ventilating the hydraulic system (1). A hydraulic system (1) carries out such a method, having a pump (2) which can be driven in a first direction of rotation (3) for a volume flow function and can be driven in a second direction of rotation (5) for an actuation function.