* Faulty Radiator Cap: A faulty radiator cap can't maintain proper system pressure. This allows coolant to boil over and escape, especially when the engine is off and the pressure slightly reduces. This is a relatively cheap and easy fix to check first.
* Head Gasket Failure: This is a serious problem. A blown head gasket allows combustion gases to enter the cooling system, creating pressure that forces coolant out. This often leads to a milky white substance in the engine oil (indicating coolant mixing with oil) or bubbles in the radiator.
* Cracked Cylinder Head or Engine Block: Similar to a head gasket failure, a crack in the cylinder head or engine block allows coolant to escape under pressure. This is usually accompanied by other symptoms, like loss of compression or coolant leaks.
* Water Pump Issues: While a failing water pump typically leads to overheating *while* the engine is running, a very bad water pump could create pressure fluctuations which contribute to coolant expulsion when the engine is off.
* Radiator Problems: A clogged radiator or a leak in the radiator itself can restrict coolant flow and increase pressure, leading to expulsion when the engine cools.
* Thermostat Issues: A stuck closed thermostat will prevent coolant from circulating properly, leading to overheating. However, a stuck *open* thermostat might *not* cause immediate overheating, but could contribute to pressure issues if the system isn't properly pressurizing.
* Cooling System Leaks (elsewhere): A small leak elsewhere in the system (hoses, connections) might not be immediately apparent but could contribute to a pressure buildup when the engine is hot.
What to do:
1. Check the radiator cap: This is the easiest and cheapest thing to check first.
2. Inspect hoses and connections: Look for any visible leaks or cracks in hoses and connections.
3. Check the coolant for signs of oil: A milky or oily appearance suggests a head gasket or crack.
4. Pressure test the cooling system: A mechanic can perform a pressure test to pinpoint leaks that aren't easily visible.
5. Inspect the radiator: Look for any leaks or blockages.
Important Note: Driving with an overheating engine can cause severe and expensive damage. If your Cadillac continues to overheat, stop driving it immediately and have it towed to a mechanic for diagnosis and repair. Ignoring the problem could lead to a blown head gasket, cracked engine block, or other catastrophic engine failure.
