I don’t know why the method of finding leaks in fuel tanks should not work for the seal. But read this and it might give you an idea of how to find the leak without smoke, water – anything other than a non-volatile gas.

 

Realize this hasn’t been tested on a seal so it may be only a “good thought” of getting it done.

Use of a Freon sniffer.

Purge the seal. Flush the inside of the seal with Freon, pressurize it a tiny bit just to have excess Freon in the line, seal it (reconnect it to the pump line), then use a “sniffer” to detect the very smallest micro leak. OK, so there are not two ends of the seal – that is you can only flow gas into the seal but not through the seal. Now, you’ll have to use some ingenuity in getting the Freon into all of the seal. Vacuum?

 

Flow plenty of air over all areas for a while to remove residual Freon pockets after putting Freon in the seal and before your search begins. Now if you find a leak using a sniffer, you might have an air leak there too. Just make sure there’s positive pressure (tiny amount) in the seal when searching for that micro amount of Freon. If you close the door and then pressure up the seal with Freon, use the sniffer around everything to find the leak.

 

CAUTION: Freon is not a life supporting gas. Don’t make the mistake of filling the pressurized cockpit with a gas that doesn’t support life. Test the sniffer with a small amount of Freon first to make sure it makes plenty of noise in the presence of Freon. Then if the sniffer is making noise all the time, get out and start again by purging everything with air. The sniffer I used is sensitive enough that purging takes a while to get rid of all residual Freon. I didn’t have a pressurized cockpit to deal with so this may not be an ideal method. But it works for finding leaks in tanks.