Why would a mercury grand marquis steam from the motor what smells like radiator fluid when overheating light come on?

If your Mercury Grand Marquis is steaming from the motor with a smell like radiator fluid when the overheating light comes on, it strongly suggests a leak in the cooling system. The steam is coolant (which often contains antifreeze, hence the sweet smell) turning to vapor due to the heat of the engine.

Several possibilities exist:

* Leak in the radiator: A crack, hole, or damaged hose connection in the radiator itself is a common culprit. This allows coolant to escape.

* Leak in a hose: The hoses connecting the radiator to the engine, water pump, etc., can become brittle, cracked, or detached over time, leading to leaks.

* Water pump leak: The water pump circulates coolant. A failing water pump seal can leak coolant.

* Head gasket failure: This is a more serious problem. A blown head gasket allows coolant to mix with engine oil or enter the combustion chamber, leading to significant overheating and potentially other serious engine damage. This is often accompanied by white smoke from the exhaust.

* Cracked engine block or cylinder head: In severe cases, a crack in the engine block or cylinder head can cause a coolant leak. This is a very expensive repair.

What to do immediately:

1. Pull over safely and turn off the engine immediately. Continuing to drive with an overheating engine can cause catastrophic damage.

2. Do NOT open the radiator cap while the engine is hot. The pressurized coolant can cause severe burns.

3. Let the engine cool completely. This may take several hours.

4. Have the vehicle towed to a mechanic. Diagnosing and repairing a cooling system leak requires professional expertise. Ignoring the problem will likely lead to much more expensive repairs later.

Determining the exact source of the leak requires a thorough inspection by a mechanic. They will likely pressure-test the cooling system to pinpoint the location of the leak.