I am in the process of removing the head from a 2010 1.8L Civic. Two rocker cover bolts snapped off in the threaded portion and I found another one with a snapped off head.
Now I am at the point of removing the head bolts, and the first two I have tried are acting like they may be about to break, too. Is there any way to ensure this doesn't happen? I am doing it manually and probably went 1/8 of a turn on each. Squeak and solid resistance. Would it be better, or just plain stupid, to try an impact? I REALLY don't want broken head bolts in the block.

Please advise.

 

Not seeing any recourse, I finally decided to try the old tried-and-true method of shocking the threads, since I couldn't access the threads with penetrant, or safely use a torch.
Using a 1/2" drive extension, a small sledge hammer, prayers, caution, and a lot of luck, I managed to remove them all without any breaking!
I beat on the heads, with the extension as a drift, numerous times each. Then, using a breaker bar, I rocked them back and forth about an 1/8th of a turn several times. A small snap and voila! Success!!
Now I need to go change my underwear.

 

That sounds like a nail bitter for sure. I hate breaking off bolts, and rarely have success getting broken ones out. Shocking them is probably what I would have suggested.

 

Yeah, I think shocking them is a good technique - most of the time. Breaks the 'seal' which has built up over the years.

You can also try slightly tightening them, before loosening them. It has the same effect, ie breaks the long-term grip of the threads.

Unfortunately, some bolts will always be just too tight and corroded and will not come out. That's when the real problems start!

Pleased you got them out okay.

 

ya scared of breaking bolts too, was gonna change out my plugs, but a buddy tried changing his plugs and one broke off into the engine. he tried to get all the **** out but about a month later the engine failed(cost him 2000 to get a new engine installed). but decided since they are working fine no bother trying.