Shim for plugging the blind cavity of a sleeve

A shim for plugging a sleeve defining a blind cavity, the shim comprising:

• a body comprising a rod, the body being suitable for being placed in an inserted position in which the rod is inside the blind cavity;
• a seal extending around the rod, the seal being suitable for plugging an annular space provided between the rod and the sleeve and for defining a chamber with the rod and a bottom of the blind cavity while the body is in the inserted position;
• a passage passing through the body for conveying air between the chamber and the outside of the sleeve, when the body is in the inserted position;
• a closure system suitable for adopting, while the body is in the inserted position:
• a closed configuration in which the closure system closes the passage, so as to fluidically isolate the chamber from the outside of the sleeve;
• and
• an open configuration in which the closure system enables the passage to convey air between the chamber and the outside of the sleeve.