I went to replace my thermostat today and snapped off one of the bolts holding the thermostat housing to the cylinder head. It snapped clean off flush with the head. I have never had to deal with this before (guess I've been lucky) what are my options in getting it out? I've heard of easy outs and reverse drill bits but have never used either one so I am unfamiliar with both methods. I suppose I could always drill the bolt out and re-tap the head as well but I think I should save that for a last resort. Any advice would be greatly appreciated...

 

You listed 2 of the most common ways to remove it. A reverse twist drill bit may very well work by itself. If the left hand twist doesn't loosen and spin the bolt out, you have a hole for an EZ out, also called a screw extractor.

I personally usually weld a nut to the broken stub with a MIG, but if you aren't equipped to do that, it's not an option for you.

 

So you would recommend trying the reverse drill bit first?

Welding a nut to it is not really an option because there is no stub sticking out to weld to. I wish there was, that would probably be the way to go...