I've had that happen on several Fiero's. Seems to be a common issue when removing the sway bar. I originally tried drilling them out with some titanium tipped drill bits but they kept breaking and it took forever. Then I found that if you use a cobalt drill bit it goes right through sooooo much easier. Once I drilled out the old bolts I just replaced them with a hardened bold and nut. I autocross my car and never had any break on me so it's working. There are holes on the side frame rails near where the sway bar bolts are attached so you can stick the nuts in through there and use your finger to help get them started while wrenching the bolt. Once it gets to tight for your fingers you can use the open end of a wrench to stick in the hole to hold the nut until the bolt is tightened with a wrench. Just make sure the holes you drill (if not exactly where the broken bolt is) will line up with the holes on the sway bar bracket before you drill them through.
Had the same problem. Used a Cobalt drill bit and drilled out the bolts. I enlarged the hole slightly, and then used heavy duty / high strength bolts that I fed through the top (through the little access hole) and then just used a nut on the underside.
Note, this was on a car that was 99% rust free except for some surface rust on the control arms. Basically... no rust.
Don't any of you guys use penetrating oil to prevent these type of issues? (...assuming you never had the opportunity to use anti-seize on these fasteners when they were assembled.)
Hah, I did... promise... but it's hard for the penetrating oil to fight gravity. Truth be told though... my Fiero is 100% rust free (had to brag). There is NO rust on it except a bit of surface rust. But those bolts... they just wouldn't give. I've literally (in the literal sense of the literal word) taken apart the whole rest of the car, and nothing else snapped!
Should have asked before I broke them. My basic problem was I didn't know about the access holes before I started. Put PK blaster on from the bottom but that did get at the treads. So will take the advice and drill them out.