Take the tank out, completely clean to bare brass where it has broke apart. You can then solder it back together. It will require radiator solder 50/50 acid core is best and some flux. I just use a propane torch and a wet sponge or rag. It will take basic soldering skills. Just make sure you have bare brass where you want the solder to go. I like to tin both pieces apart, get them completely covered with solder, and then put them together and heat them until the solder flows and the parts go together. Keep your wet sponge or non synthetic rag handy to wipe down and cool your pieces. Watch getting the tank to hot near the seam, you may melt the solder out there, no problem, just resolder the seam also. It is real easy to fix. You can get the best looking paint at Eastwood Co. for the tank and radiator. It is called radiator paint. It looks better than the high temp paint usually sold for some reason.