Method for operating a drive train , with 1.1 a primary drive machine ; 1.2 a work machine which is driven by the former; 1.3 a hydrodynamic coupling between the drive machine and the work machine ; 1.4 a temperature detection device for detecting the temperature in the hydrodynamic coupling , 1.5 in at least the case of a change in the load state and/or operating state of the drive train , the temperature of the hydrodynamic coupling being detected at the time of the change, 1.6 a temperature profile to be expected being calculated in a manner which proceeds from the detected temperature and the new load state and/or the new operating state of the drive train , 1.7 a warning signal and/or a stop signal for the primary drive machine being output if the temperature of the calculated temperature profile exceeds a predefined maximum temperature (θ 3 ) within the duration to be expected of the new load state and/or the new operating state, and characterized 1.8 in that, in the case of a change of the operating state from a switched-on to a switched-off state of the primary drive machine , a start-up temperature profile of heating in the case of starting up of the drive train is additionally calculated in a manner which is based on the load state at the time of the switch-off, from which start-up temperature profile a maximum occurring start-up temperature difference is determined, waiting until the calculated temperature profile has reached an enabling temperature which undershoots the maximum temperature by at least the start-up temperature difference being carried out before the enabling of renewed starting up of the drive train . 1.1 a primary drive machine ; 1.2 a work machine which is driven by the former; 1.3 a hydrodynamic coupling between the drive machine and the work machine ; 1.4 a temperature detection device for detecting the temperature in the hydrodynamic coupling , 1.5 in at least the case of a change in the load state and/or operating state of the drive train , the temperature of the hydrodynamic coupling being detected at the time of the change, 1.6 a temperature profile to be expected being calculated in a manner which proceeds from the detected temperature and the new load state and/or the new operating state of the drive train , 1.7 a warning signal and/or a stop signal for the primary drive machine being output if the temperature of the calculated temperature profile exceeds a predefined maximum temperature (θ 3 ) within the duration to be expected of the new load state and/or the new operating state, and characterized 1.8 in that, in the case of a change of the operating state from a switched-on to a switched-off state of the primary drive machine , a start-up temperature profile of heating in the case of starting up of the drive train is additionally calculated in a manner which is based on the load state at the time of the switch-off, from which start-up temperature profile a maximum occurring start-up temperature difference is determined, waiting until the calculated temperature profile has reached an enabling temperature which undershoots the maximum temperature by at least the start-up temperature difference being carried out before the enabling of renewed starting up of the drive train . <EOS>