SEALING PLUG

PURPOSE:To suppress the generation of rust and to hold the airtightness of liquid, by providing a threaded part, which is screwed to the larger contour part of an injection port, and a rubber cap which is stopped to the point end of the threaded part while forced to be press fitted to the smaller contour part of the injection port sealing the liquid. CONSTITUTION:A sealing plug 1, inserted into an injection port 42, screws a threaded part 32 in a stop thread part 3B to a threaded part 53 provided in a side of the injection port 42, and tightening this stop thread part 3B, the sealing plug 1, in which a stopper part 3A of a screw main unit 3 presses an inner side wall surface 23 of a rubber cap 2, deforms it in such a shape that one end 2a of the rubber cap 2 advances into a smaller contour part 52 of the injection port 42. While the sealing plug 1 is sealed in a condition that it holds air-tightness by deforming the rubber cap 2 in the lateral direction so that its side surface part 26 is forced to be attached to a wall part 55 of the injection port 42. In this way, the sealing plug 1, which advances the rubber cap 2 to be pressed to the small contour part 52 in the point end part 51 of the injection port 42, prevents cooling liquid from its leakage from the injection port 42. While the screw main unit 3, coming into no contact directly with the cooling liquid, is prevented from the generation of rust or the like.