* Head Gasket Failure: This is a very common cause. A blown head gasket allows coolant to leak into the combustion chamber (causing white smoke from the exhaust and potentially milky oil) or into the oil pan (causing milky oil). It's the most likely explanation if the coolant level drops steadily.
* Cracked Cylinder Head or Engine Block: Similar to a head gasket failure, cracks in the engine's metal allow coolant to escape internally. This is usually less common than a head gasket failure but still possible, especially in a higher-mileage vehicle like a '93 Caravan.
* Coolant Leak into the Transmission (rare): While less frequent, a severe internal leak could allow coolant to mix with transmission fluid. This would likely be accompanied by other symptoms, like transmission problems.
* Internal Coolant Leaks in the Heater Core: The heater core is inside the car's dashboard, so a leak here might not be immediately obvious. You might notice a sweet smell inside the car or damp carpets.
* Porous or Damaged Hose (internal degradation): While you're checking external hoses for leaks, the inner lining of a hose can degrade over time, leading to slow internal leaks, which are difficult to detect.
How to Diagnose:
You'll need to get a more thorough inspection. A mechanic can:
* Pressure test the cooling system: This helps pinpoint leaks, even internal ones.
* Inspect the oil for signs of coolant contamination (milky appearance): This is a strong indicator of a head gasket or crack.
* Check the exhaust for white smoke: Another symptom of a head gasket problem.
* Examine the coolant for signs of oil contamination: Oil in the coolant can also indicate a head gasket or crack.
* Look for other signs of overheating: Is the engine running hot? Does the temperature gauge climb?
Important Note: Driving a car with a suspected head gasket failure or internal coolant leak can cause serious engine damage. It's crucial to have it checked by a mechanic as soon as possible.
