You can do yes, however it is rather an involved process, and we would need to know more about what sort of cast iron housing it was. Cast iron often needs all sorts of pre heating, either in a kiln or with several blow torches or propane flames. Otherwise the weld will crack. Others more knowledgeable than me will surely answer in more detail though.
Brazing is less likely to crack than welding. Also drill each end of the crack to stop it spreading. You could also consider metal stictching, which is a cold process.
Do you think I could fill this hair line crack after grooving it. I need to make it water tight but also for min. strength too. I was not sure if flux coated bronze would stick to cast iron. See pic.
p.s. I am using a 1500F. oxy/mapps torch.
Groove it out pretty deep and fill it in with brass rod. You should give it a little preheat and wrap it with insulation after welding so it cools slow....Bob