The paper discussed the repair of internal combustion engines. For the purposes of understanding the above, internal combustion engines, their development, fuel quality, mechanics and elements of internal combustion engines, the principle of operation of internal combustion engines, diesel engine glow plugs, diesel engine exhaust, engine cooling system and heat transfer were defined. the lubrication system, the ignition system of the internal combustion engine, and the future of the internal combustion engine. Internal combustion engine repair and damaged parts repair process, car engine repair methods: magnetic fault detection for crankshaft checking, decarbonization, "bumper block purchase" repair method, "cylinder block liner and original pistons" repair method, and repair method were further analyzed. "original bore liners and larger pistons", and explained internal combustion engine repair technologies. The paper presents an example of repair from practice: a Perkins D 4.203 internal combustion engine, by measuring deviations on the cylinder liners and pressing the liners outside, measuring the overlap of the cylinder liner and the bore of the engine block and pressing inside, and leveling the base of the engine block, turning and honing of the cylinder liner.