Broke my water pump bolt. Now what? (Update - broken bolt is out)

After spending over 40 years in maintenance in the food industry, I have seen many mechanics heat the broken bolt and then quickly grab hot softened steel and try to turn it. The result is obvious, it doesn't work! Heat the bolt red hot as best as you can and walk away, let it cool and shrink, then attempt to turn it.
Cast iron does not expand when heated as steel does. Use this to your advantage as steel, when hot enough, expands and is constrained inside the cast iron, then shrinks as it cools. If the bolt is long and deep, only the part that got hot enough to shrink when cooled will release from the casting. I used a brazing tip of my acetylene torch to concentrate the heat.
Remember, steel in cast has advantages..
Good luck.