temporary or limited seal results from the upset 42 engaging the first annular surface 30 the axial surface 32 or both for example depending upon tolerances tightening the fastener 18 and corresponding connection plate 16 compresses the upset 42 against one of the surfaces of the counterbore 28 and creates a temporary or limited seal prior to filling the system with refrigerant a leak test that includes drawing a vacuum on the system is conducted the temporary or limited seal is often sufficient to result in the a c system passing the leak test accordingly the a c system is filled with refrigerant which over time leaks out causing repair and warranty concerns as illustrated in fig6 the slot 50 provides a predetermined leak path illustrated by the arrow 56 accordingly when the o ring 46 is missing the leak testing equipment cannot draw a vacuum as it draws air through the slot 50 into the a c system during the leak test since drawing air through the slot 50 prevents drawing a vacuum the slot 50 provides a mechanism whereby the a c system does not past the leak test if the o ring 46 is missing accordingly the present invention provides a leak detection mechanism in the form of a passageway or slot 50 extending between the seal surface 54 that portion of the second annular surface 34 contacted by the o ring 46 and the outer surface 22 of the component 20 the passageway or slot 50 is only open or communicates with the interior of the.