Fix broke thermostat cover bolt on '89 525?

[Gene in NC]

First bolt broke, expect others same. Anyone had success with stub extraction?
Dealer cost for thermostat housing and gasket about $65 w tax plus order time.

Plan to use stainless as replacement.

[Ross]

You can try heat, they are smaller bolts so a mapp gas torch ought to be hot enough. If they break you'll likely need to drill and retap. Sometimes, not often, if you manage to center the bit correctly and use a bit just a hair under the root size of the bolt the old threads will relax their grip and you can turn the hollow bolt out.
Good luck