I would fill them with beer and force carbonate them only to find that most of the gas leaked out within 12 hours or so leaving me with well made, but flat, beer.
I have avoided doing anything about the problem and focused on bottle conditioning.
This weekend I decided to package my Octoberfest in bottles to keep from ruining it in a leaky keg.
Anyway I googled some kegging stuff and decided to re-build my 3 Cornelius kegs.
I immediately ordered a dip tube brush, new O-rings and some Keg Lube from a reputable homebrew supply.
When the stuff got to the house I scrubbed the vessels clean with Oxy Clean.
Oxy Clean is a 2-sided coin.
It's fairly inexpensive and does a good job but you need to rinse it off very well. I mean really rinse it off.
I let the kegs soak overnight and took them apart before scrubbing the inside, outside, lids, dip tubes, connectors and poppets.
These kegs are holding gas well, even at a fairly low PSI.
I feel accomplished.
I can't wait to get some beer made so I can test my new draft skills.
Good beer to you.