Purpose: To research the possibility of diagnostics of power unit elements in specialized railway rolling stock using passive thermal control technology. Methods: The following analyses were conducted: an assessment of the technical condition of the specialized railway rolling stock and internal combustion engines; an experimental study of the thermal field; and a comparative analysis of internal combustion engines with different technical parameters. Thermal imaging studies were carried out on two structurally similar YAMZ- 238 engines. Results: The method of passive thermal control has been selected following a thorough analysis of faults and their diagnostics. The results of thermal imaging control of internal combustion engines in a fully serviceable condition, as well as those with different faults, have been described. It is concluded that there is potential for the implementation of thermal imaging control in the context of routine and field inspections of rolling stock. The thermal maps obtained provide an accurate diagnostic tool for the assessment of the technical condition of internal combustion engines and enable the identification of potential failures at different stages. Comprehensive thermal imaging control of internal combustion engines was carried out by taking pictures of internal combustion engine systems and detecting the presence or absence of malfunction in them. During the diagnostic process, the cooling system, fuel system, engine body and air-ignition system were subjected to thermal imaging. During the diagnostics, the external temperature of elements and their hermeticity were thoroughly controlled both within the body of the investigated part and in the points of their connection with other elements. Practical significance: A promising method of controlling the technical condition of internal combustion engines of railway rolling stock and their malfunction detection has been proposed. The research has been carried out, confirming the expediency of thermal imaging control application. The future accumulation of heat map data on engines in different technical conditions will allow for accurate fault detection and identification of its underlying cause, without the need to disassemble the internal combustion engine.