Q: Bolt broke by thermostat

There are a lot of malfunctions that can cause a car to overheat. Low coolant level, worn water pump, sticking thermostat, internally clogged radiator, externally clogged radiator, improper cooling fan operation, sludge coated water jackets, collapsed hoses or bad head gaskets. The thermostat is a good place to start, but they can be checked without removing them. The 3.8 in your car has a history of bad head gaskets. It’s also possible that your temp gauge is malfunctioning. A thorough diagnostics is needed to inspect all the parts of the air flow and coolant flow systems. A snapped off bolt can be troubling. Steel bolts can seize and corrode when threaded into aluminum. Heat is usually required and a bolt extractor kit. A qualified mechanic from YourMechanic can come out to diagnose the overheating issue and inspect your thermostat.