a fuel cell system with reduced leakage and a method of assembling a fuel cell system . bipolar plates within the system include reactant channels and coolant channels that are fluidly coupled to inlet and outlet flowpaths , all of which are formed within a coolant - engaging or reactant - engaging surface of the plate . one or more seals are also formed on the fluid - engaging surface to help reduce leakage by maintaining fluid isolation of the reactants and coolant as they flow through their respective channels and flowpaths that are defined between adjacently - placed plates . the seal — with its combination of in - plane and out - of - plane dimensions — forms a substantially hollow volume , into which a plug is placed to reduce the tendency of the seal to form a shunted flow of the coolant or reactant around the intended active area of the plate . a fluid port intersection is integrally formed with the seal and is formed to be fluidly cooperative with the volume , and is capable of accepting the introduction of a fluent precursor of the plug material such that upon curing , the precursor material forms a substantially rigid insert that continuously fills both the volume and intersection , thereby increasing the resistance of the plug to movement and the seal to shunted flow . in one form , the geometry of the fluent material injection site is such that it promotes plug anchoring within its intended location , while also providing a manufacturing aid to visually inspect for plug installation , as well as to serve as a bipolar plate stacking alignment locator and verification .