Method for operating a fluid line device having a first line section in a warm region and a second line section, connected thereto, in a cold region, wherein in the first line section a pump for conveying fluid is arranged, comprising activation of a pump start-up program when the pump is activated, wherein the pump start-up program comprises the following steps: A) predefining a fluid quantity to be conveyed; B) starting a fluid introduction sequence, including conveying the predefined fluid quantity from the first line section into the unfilled second line section; C) starting a fluid return-flow sequence, including flowing back of the fluid quantity introduced into the second line section into the first line section, and determining a return flow temperature of the flowing-back fluid in the first line section; D) increasing the predefinition of the fluid quantity to be conveyed, and carrying out one of the following substeps; d1) repeating the steps A) to D) if the return flow temperature of the flowing-back fluid is higher than or equal to a return flow limiting temperature, and the increased predefinition of the fluid quantity to be conveyed is less than or equal to a limiting quantity; d2) deactivating the pump start-up program and commencing normal operation of the pump if the increased predefinition of the fluid quantity to be conveyed is larger than the limiting quantity; d3) deactivating the pump start-up program, deactivating the pump and resetting the predefinition of the fluid quantity to be conveyed, if the return flow temperature undershoots the return flow limiting temperature. A) predefining a fluid quantity to be conveyed; B) starting a fluid introduction sequence, including conveying the predefined fluid quantity from the first line section into the unfilled second line section; C) starting a fluid return-flow sequence, including flowing back of the fluid quantity introduced into the second line section into the first line section, and determining a return flow temperature of the flowing-back fluid in the first line section; D) increasing the predefinition of the fluid quantity to be conveyed, and carrying out one of the following substeps; d1) repeating the steps A) to D) if the return flow temperature of the flowing-back fluid is higher than or equal to a return flow limiting temperature, and the increased predefinition of the fluid quantity to be conveyed is less than or equal to a limiting quantity; d2) deactivating the pump start-up program and commencing normal operation of the pump if the increased predefinition of the fluid quantity to be conveyed is larger than the limiting quantity; d3) deactivating the pump start-up program, deactivating the pump and resetting the predefinition of the fluid quantity to be conveyed, if the return flow temperature undershoots the return flow limiting temperature. d1) repeating the steps A) to D) if the return flow temperature of the flowing-back fluid is higher than or equal to a return flow limiting temperature, and the increased predefinition of the fluid quantity to be conveyed is less than or equal to a limiting quantity; d2) deactivating the pump start-up program and commencing normal operation of the pump if the increased predefinition of the fluid quantity to be conveyed is larger than the limiting quantity; d3) deactivating the pump start-up program, deactivating the pump and resetting the predefinition of the fluid quantity to be conveyed, if the return flow temperature undershoots the return flow limiting temperature.