The crack was indeed around a stud but extended to a couple of inches beyond that. I don’t think it was leaking. And in removal a bit broke off. Fortuitously I had a replacement. It was a devil to get the old one off - three studs snapped. But it’s done now and it doesn’t leak. And we’ve just returned from a 1400 miles road trip in France. It was unbelievably hot but BTA didn’t overheat. I had to adjust the contact/breaker points once - not sure this was my fault or the high temperature or poorly made points.