A method for closing an end part of an aluminium heating radiator element, comprising the steps of: - providing a substantially tubular body, made of aluminium and provided with an inner chamber for water circulation and comprising a substantially tubular end part that extends along an axis and has a bottom opening delimited by an end edge; and a cap shaped so as to close the opening; the end part and the cap being provided with respective melting portions (21, 22) having respective contact edges (23, 24); - placing the end part and the cap in a mounting configuration, in which the end part and the cap contact each other via the respective contact edges (23, 24) to form an assembly; - performing a thermo-electric melting process of the assembly, in which the melting portions (21, 22) contacting each other via the respective contact edges (23, 24) melt and join intimately to make a monolithic piece; - wherein the thermo-electric melting process comprises the steps of: positioning the cap on a first element and the end part on a second element, which slide with respect to each other; connecting the cap and the end part to respective electrodes (41, 42); circulating a current of preset intensity through the assembly among the electrodes (41, 42), and applying an axial thrust for pushing the end part and the cap one against the other during the passage of current; the first element comprising a pushing member which moves along an axis and which carries a first electrode, which supports the cap, while holding said cap; a second electrode being arranged above the second element and being movable vertically to be carried to contact the end part so as to distribute the current on the whole part which is to be melted; and - wherein in the mounting configuration the contact edges (23, 24) of the end part and the cap have substantially equal shape and dimensions and the electrodes (41, 42) are arranged so as the contact edges (23, 24) reach the melting state at the same time. - providing a substantially tubular body, made of aluminium and provided with an inner chamber for water circulation and comprising a substantially tubular end part that extends along an axis and has a bottom opening delimited by an end edge; and a cap shaped so as to close the opening; the end part and the cap being provided with respective melting portions (21, 22) having respective contact edges (23, 24); - placing the end part and the cap in a mounting configuration, in which the end part and the cap contact each other via the respective contact edges (23, 24) to form an assembly; - performing a thermo-electric melting process of the assembly, in which the melting portions (21, 22) contacting each other via the respective contact edges (23, 24) melt and join intimately to make a monolithic piece; - wherein the thermo-electric melting process comprises the steps of: positioning the cap on a first element and the end part on a second element, which slide with respect to each other; connecting the cap and the end part to respective electrodes (41, 42); circulating a current of preset intensity through the assembly among the electrodes (41, 42), and applying an axial thrust for pushing the end part and the cap one against the other during the passage of current; the first element comprising a pushing member which moves along an axis and which carries a first electrode, which supports the cap, while holding said cap; a second electrode being arranged above the second element and being movable vertically to be carried to contact the end part so as to distribute the current on the whole part which is to be melted; and - wherein in the mounting configuration the contact edges (23, 24) of the end part and the cap have substantially equal shape and dimensions and the electrodes (41, 42) are arranged so as the contact edges (23, 24) reach the melting state at the same time.