the invention relates to a process for manufacturing a thermoplastic part with an injected seal as well as to an injection molding apparatus and a corresponding thermoplastic part . for injecting the seal , a groove is formed during molding of the thermoplastic part in which groove liquid crosslinked plastic as material for the seal is injected . sealing projections are formed on the groove edge and / or on the injection mold in order to prevent an overflowing beyond the groove edges during injection . when closing the mold , undercuts are formed on the upper edge of the groove for holding the solidified seal in the groove .