Thanks to Richard K for contributing to this FAQ!
Recently, I broke off the bolt to the thermostat housing unit and triedvarious things getting it out including bolt extractors(two types) to no avail. So I asked an old mechanic (73 years old) what should I do to get it out and he said "Get yourself a small propane torch and heat that bolt forabout 5 minutes until it's good and hot, until it turns red-hot. Then get a good pair of vase-grip pliers and clamp it on that bolt and turn it back and forth (clockwise and counter-clockwise) and I guareenty you that that bolt will come out". I did exactly what he suggested and after about 10-15 minutes I had it out. You can also drill it out and use an easy-out to get it out as well.
Thanks to Jon T for contributing to this FAQ!
IMO, avoid so-called "easyout" bolt removal tools like the plague. In twenty years of turning a wrench for a living, I have never -- NOT ONCE --
heard of an easy out working as promised but I've seen others try them dozens, if not a hundred times.
If you've broken off a bolt and there's enough to get a grip on, try vice-grips. You may need to use a high-speed grinder or cut-off tool to cut
a slot in the end of the bolt shaft, so that you can remove it with a screwdriver.
If the bolt is broken off flush (as is commonly the case), take a smaller diameter bolt and, using a MIG welder, weld the small bolt to what's left of the broken bolt. Back it off steadily.
If you're skilled with the welder, you can even "build up" the head of the broken bolt above the surface, then try the other approaches.
Worst case, you'll need to drill out the remnants of the bolt and rethread the hole. (Unless you're very, very careful and skilled whereby you can
drill out the bolt precisely and remove the remnants with a pick. I've seen it done but it's a challenge to say the least).
But don't bother with easyouts. All they'll do is break off and leave you $6 poorer, and leave you with a stub that's too hard to drill or weld.
Thanks to John D. for contributing to this FAQ!
If you have broken bolt, and you have enough to grip,try putting a Fat washer then a Nut to fit on the broken bolt then weld the nut to the broken, Ive done this thousands of time and it works great.