Holy bellows! A large percentage of the older bellows-cameras I see has pinholes in the corners. In fact, I have seen bellows-cameras with the bellows looking almost new, yet having plenty of holes that only showed up with the below-mentioned darkroom inspection method. If your bellows has so many holes that you can't count them, bite the bullet and get a new replacement.

What - only a few holes? Be advised that they may multiply like rabbits, but you can get along for a long time with patching. Forget the tape. Forget the silicone. Find a proper bellows patching compound [OURS!] which can be applied to the inside corners which bear holes, and that will set both dry and flexible. Paint some on other corners where holes are likely to appear.

Fortunately, most of the issues can be checked with one test. Take the camera and mounted lens into a room that can be made totally dark - this might be only at night. Stick a 25 watt or so light bulb on the end of an extension cord [it may require a socket-to-wall-socket adapter from the hardware store]. Do NOT place the lit bulb directly on the bellows, but prop it up on something; I find a roll of masking tape works well. This is usually most easily installed through the removed ground glass back. Close the shutter or cover the front of the lens - also drape a dark cloth over the rear. [I am reminded that a good technique is to insert a film holder in the back]. Now turn out the room light and sit tight for five minutes until your eyes become very light sensitive. Examine the camera bellows, area around the edge of the lensboard, and also around the lens flange! If you can't see anything, all is well. Otherwise mark the pinholes with a white Stabilo [tm] or other marker that will allow you to find the spots later, when patching.