Abstract: An engine component of the type having a cavity therein through which cooling water can circulate, there being ports which lead from a face of the engine component into the cavity, is pressure tested by closing the ports and by pressing port closing elements onto the face so as to blank off the ports. The cavity is then pressurised and the engine component observed for seepage of water or the appearance of bubbles. The port closing elements are pressed onto the face by means of a transparent, laminated glass plate which is held in a steel frame by means of an elastomeric adhesive. Between the glass plate and a pressure bearing face of the steel frame there is a layer of elastomeric material.