2003 Mercury Grand Marquis. Overheated. Car is "like new, less than 96,000 miles.
Now check engin light stays on. What to do?

 

First, disconnect the NEGATIVE battery cable for 30 minutes -- then re-connect the cable.
Check the coolant level and fill to the "COLD" line before starting the engine.
Start the engine and watch for signs of leaks as the engine warms up.
You will have to determine why the engine overheated in the first place.
Replace Thermostat with STOCK Temperature unit (192-195 degrees F.), if necessary. Motorcraft RG-571 is correct gasket, goes ON TOP of thermostat -- Thermostat is installed with Springs DOWN.