The engine may overheat at idle when the AC is on. A new, upgraded fan motor and resistor assembly should be installed.
Problems for specific Ford Crown Victoria years:
Car problem reports
Problem with your car? See what our experts say or submit your own.
Repairpal verified 2003 Ford Crown Victoria problems
The composite (plastic) intake manifold may crack near the thermostat housing and cause a coolant leak. Ford released an updated manifold that was reinforced to prevent a recurrence. No recall was issued for this problem but Ford did extend the warranty to seven years on some models from the date of purchase.
Catalytic converter failure is common. Internal components become loose, causing a rattle or creating back pressure in the exhaust.