A venting cap system includes a first open-ended sleeve and a second open-ended sleeve. The first open-ended sleeve is made from a first material that melts at a selected temperature. The first open-ended sleeve has an internal region commencing at a first end and an externally-threaded region commencing at a second end. The second open-ended sleeve is made from a second material that does not melt at the selected temperature. The second open-ended sleeve is coaxially fitted in the first open-ended sleeve. The second open-ended sleeve includes a first end that is flush with the first end of the first open-ended sleeve. The second open-ended sleeve partially overlaps part of the externally-threaded region. The coefficients of linear expansion of the first material and the second material are about equal.