When I went looking for parts to rebuild a compass the manufacturer strongly recommended that I let an authorized service rep do the work. They indicated that a pressure test was required to locate the leak. I did not heed the advice, purchased the glass and "O" rings and a bottle of compass oil (mineral oil)........ and it did not work after a couple of weeks I had an air bubble the size of a half dollar. It was not a total loss as I had fun hunting for the parts, taking it apart and putting back together and learned a valuable lesson. Take it to a pro.