[Mr.NutCase]

I overtighted a bolt on a 1993 Altima, broke the "air bleed crew/cap,it is by the themostat hausing, the socket size is a 10mm, How hard would it be to remove the bolt

[abuseddog]

It might be too small to use an easy out. I might just try drilling it out then puttin a bigger tap through it

[Henry Highrise]

Sometimes just using a left handed drill bit will bring one out.

[Huskinhano]

How tight is the remaining bolt in the manifold? I've used electric engravers to back out broken bolts/studs. The vibration loosens things up to a point. Just do it in a counter clockwise rotation. This may work. Some times a using a center punch tapping it works also. One last desperate thing to try is welding a bolt or a nut on to what's remaining of the old bolt. That way you have something to grab.

[ChevelleSS_LS6]

make a screw with a dremel tool

[GearJamminHero]

I have used easy out's from Craftsman for bolts as small as M6. You should be able to use an easy out no problem, the one you broke is probably M8. The left handed drill bit mentioned previously works a good deal of the time as well! Just make sure your drill is in reverse.