Abstract: A fluid circuit for a hydrodynamic coupling comprises a circuit line which is connected to the outlet of the coupling and which extends via a cooler and via a flow control element back to the inlet of the coupling. An overflow valve serving for limiting pressure and the delivery line of a filling pump are connected to the circuit line in front of the flow control element in the flow direction. Arranged in the delivery line are a fixed-setting throttle element, for example a diaphragm, and, parallel to this, a high-speed filling valve which opens automatically when the pressure prevailing in the circuit line in front of the flow control element falls below a specific limiting value.