How do you take a thermostat out of a 2001 mercury grand marquis if the bolts are very tight?

To remove a thermostat from a 2001 Mercury Grand Marquis when the bolts are very tight, first ensure the engine is cool and disconnect the battery. Use penetrating oil on the bolts and let it sit for a while to help loosen them. Apply a socket wrench or a breaker bar for extra leverage, and consider using heat from a heat gun or torch cautiously to expand the metal slightly, which can help break the bolts free. If necessary, use a bolt extractor as a last resort to remove any stubborn bolts.