Just bought a new radiator thru speedway auto parts. It's a spectra premium. I had to get a new one because mine cracked at the top neck and along the bottom. I installed the new one today, and it leaks from the exact same spot on the top neck. I tried to solder the last one and it didn't hold. Are these radiators notorious for this? I don't know what I'm doing wrong, but I'm to the point where I'm extremely frustrated. Somebody please help!