Yes and no. Some crowns are designed so that the O-ring is easily replaced. Most of Omega's screw down crowns are this way, where I can simply go in and pull the O-ring out with tweezers or using a small pick (made from a broken oiler).
For the type of crown that is typically used on Speedmasters, it's not that simple. Here's what a worn out seal in a crown looks like:
As you can see there is a post coming up the middle of the crown that the stem screws into. The O-ring is under that washer, which is swaged in place, so to replace the O-ring there are 2 possible paths. One is if the O-ring crown section is smaller than the gap between the post and the washer, you can dig it out and push a new one in without fear of damaging the O-ring in any way. This assumes that you have the correctly sized replacement O-ring. Omega does not sell O-rings for these crowns, because they are not meant to have the O-rings replaced.
Now is a good time for a word about old O-rings. They have several stages of death. The first is loss of elasticity - they would be easy to remove at this stage. Then things get steadily more difficult, so you have serious hardening of the O-ring - honestly sometimes these are so hard you can only chip them away...like this one on a case back:
I can't imagine being able to remove these from a crown very easily just by picking them out. Then they turn to black goop, so the only way to get them out is solvents, and you would have to be 100% sure you got it all, because if you don't, then you could be compromising the water resistance of a new seal. Then if they last through the goop stage, they become like hardened bubbly black glass, and are even tougher than the video above to remove.
The second way would be to remove the washer, remove and install the new O-ring, then install the washer. I'm sure in this discussion someone will post the link to the Seiko crown where the guy stuffs a bunch of O-rings into a crown to force the washer out, replaces the O-ring, and manages to get the washer back in. So yes, it can be done - is it anything I would offer any sort of guarantee on? Not a chance.
I hear of people saying it's easy and they do it all the time, but whenever I've asked those people to tell me what size the O-ring is that they use as a replacement, I never get an answer...perhaps one of the people who say it's easy could start a business restoring vintage crowns - I'm sure they would make a killing doing it, but it won't be me...
😉
