Paul, if absolutely unable to extract them, then I would go ahead and drill them out.  Then I would retap the holes.  That might mean a slightly larger hole and bolt.  Without looking, though, I don't know if there is metal for that, which would be 10 mm if the present bolts are 8 mm.

But what do I know, and wiser, more experienced folks might say differently.

mcneely

---- Paul <wognacious@GMAIL.COM> wrote:
> As luck would have it the two 8mm, I think, bolts that are on the opposite
> side of the temp sensors in the thermostat housing sheared off due to being
> seized in the holes due to lack of maintenance on my part. Anyhow I've
> managed to drill them out to the point where I don't want to use a larger
> drill bit and risk screwing up the threads. In fact in one of the bolts I
> tried using an extractor type bit that broke off in the bolt too. Any sage
> advice would be greatly appreciated. These are the last two stumbling
> blocks, that I'm aware of now, standing in the way of me getting my engine
> back in the van so we can go camping................
> Help,
> Paul in Tracy

--
David McNeely