During start-up of hydrotronic system (hydraulic system with electric control) in low ambient temperatures a faulty operation may occur. The principles and conditions of safe operation of hydraulically (hydrotronically) driven machines and devices is essential for their designers and operators. For these reasons the author did a series of tests of hydraulic (hydrotronic) components and systems under thermal shock conditions (cooled-down components were supplied with hot working medium). In such conditions starting parameters of the selected hydrotronic components and systems, which secured safety of their operation, were determined. During start-up of a hydrotronic system under thermal shock conditions elements of hydraulic components warm up in a non-uniform way, due to varying material and shape properties. This causes change of clearances between the cooperating elements and may lead to faulty performance of hydraulic components and result in machine break-down. Heat transfer coefficients between oil and swilled element were determined and used for a calculation method developed by the author. The method enables to predict correct or incorrect operation of hydrotronic system.