snapped bolt

1988 Dodge Dakota 3.9L.Thermostat housing was leaking.I snapped one of the bolts off.There is plenty of room to drill it out but can't find a bit that will drill it.What kind of bit should I use?

Make sure you use a center punch and make a good mark. I would start with a small 1/8 inch bit. Try a cobalt drill or carbite tipped drill. You didn't break off an easy out in the bolt did you? If so you will have to order a tungsten carbite steel drill not cheap. I drilled one out in a crankshaft and this was the only drill that would touch it without going to diamond tipped.