Take an old automobile or truck innertube and cut it twice so that you have
a cylinder of innertube 6-8 inches tall or so,,,,,
Stretch that over the outside of the top of your corney and work it down
around past the black phenolic hand holes and down onto the steel....
fill the keg with gas and the top of the keg thing with water and watch for bubbles
...this submerges the entire top of a keg and allows you to submerge all the fittings and the lid...
so EZ to spot any leakage.