Managed to shear one of the bolts on the thermostat housing last night what do I need to buy to remove what's left? Or even better, anyone local want to cone do it for me? Tea and biscuits available

Is the bolt sheared flush with the housing or is there some thread exposed?

EDIT - this if its flush http://www.machinemart.co.uk/shop/product/details/cht123-screw-extractor-wrench-set

[Edited on 30/11/11 by luke]

To be honest I gave up removing it after sheering the first bolt. Does the housing have a threaded hole? I presume not. Will have a go at removing the housing tonight and see if it's flush to the block or not.

Don't use a screw extractor it's going to cause more trouble if it does not work; they have a habit of snapping not surprising if the bolt it self is sheared..

Ditto. Don't use a stud extractor. Work of the devil. They're hard and brittle which means if you give them any beans at all they snap off and then they're a right royal PITA to drill out.

Have you got a welder? Put a nut over whats left of the bolt and weld down through the nut hole. Let it cool then let rip with a big old spanner.

Good idea ben! will give that a go if its not flush!

I find lots of tapping with a small hammer helps prevent this happening, recommended on the remaining bolts.
Or an impact wrench is often a good tool.

On the broken stud if welding a nut on isn't viable, file it as flat as possible, centre punch and then drill out going up in small increments. The heat generated always helps. I have found that once the drill size is just about there, you can get the very outside layer of the bolt out, either it unscrews or can be bent and removed that way.
There are some good stud extractors available, but they are not cheap. Irwin do some tasty ones and I have a good friend who happens to be one of their reps. He has a substantial collection of their tools

Got it out today using bens suggestion, worked a treat.