First. Is it cast iron that you are welding? If so. You need to use a suitable electrode ( made for cast). Preheat the area gently with a propane torch to pre-expand the metal and prvent heat cracking. I wouldn't drain the fluid, as this will help to disipate the heat from the welder. It won't take long enough to create enough fumes to be a fire hazzard. If in doubt do it in 2 attempts rather than build up to much heat in one go.
Alternate choice. If the is a stud or bolt nearby, you might make a bracket to fastem to the bolt and attach the spring to it.