What's the best method to remove a broken bolt from the thermostat housing. -I'll try some heat, penetrating oil and vise grips first.. the move on the the welder.... Is the bypass is cast iron? the thermostat was pretty old and not closing/opening all the way.
Yes. The crossover manifold is cast iron. Whack the broken shank with moderate force a couple times, then lay a nut that fits on that broken shank and weld it, and as it turns back to dark cherry red, work it back and forth with a wrench, or with impact driver on low setting forward and reverse. If you don't have the means to weld it, you might want to pull the manifold and get it to a shop that can remove it. Does not look like enough to get a good purchase with vice grips. Galvanic corrosion may make it almost impossible to remove by drilling and using an EZ Out extractor.
I had enough old bolt to weld a nut to the top, I broke the weld 2 times before it came loose. Made sure I tapped both holes again before re-assembly. Thanks for the advice. I always hate drilling and tapping old bolts.
I just removed one of these yesterday. I used this tool: https://www.amazon.com/ARES-70016-Damaged-Extractor-Removes/dp/B01GKEBG9I There was enough of the broken bolt to grab with it... I did MAP gas the area around the broken bolt before turning it out...
After breaking the first 2 times I welded the nut I don't think that tool would have been tight enough... she was in there...
Certainly possible... It does tighten as you turn it counter clockwise, but I have broken off some other stumps with it too, and ended up drilling...