leaking black fluid indicates that you should check your:\nengine\ntransmission fluid\nair…

Brief Explanations:

Engine oil can turn black over time due to contaminants and wear - related particles. A leak of black fluid is likely engine - related. Transmission fluid is usually red or brown when new and doesn't typically appear black in normal conditions. Air conditioner refrigerant is clear and not black. Coolant is usually colored (green, orange, etc.) and not black.

Answer:

Engine