To remove a broken bolt from a car engine, first drill a hole in the bolt, and then use a bolt remover that is the right size for the bolt you are trying to remove. The bolt remover threads in a counterclockwise direction, allowing it to reach the taper of the bolt and remove it. Another option is to heat the shaft of the bolt using a propane torch, and then use strong pliers to remove the bolt.
To use the bolt remover method, create an indentation in the center of the bolt thread using a steel centering punch and hammer. Use a metal-cutting drill bit to drill a 1/8-inch hole into the bolt where the indentation is located. Measure the bolt threads to determine the correct bolt remover. Make the hole in the bolt the size recommended in the bolt remover instructions. Screw the bolt remover into the hole in a counterclockwise direction, and then use a wrench to remove the bolt.
When using the propane torch method, heat the bolt until it reddens slightly. The heat from the torch breaks the bond between the bolt threads and the other material; it also expands the metal, making it easier to remove the bolt using pliers.