Why has your coolant gone brown?

Coolant can turn brown due to a combination of rust, dirt, and debris mixing with the fluid, often indicating corrosion within the cooling system. This typically occurs when the coolant loses its effectiveness, allowing metal components to rust. Contamination can also result from a failing radiator or a breach in the head gasket, which can introduce oil or other contaminants. It's important to address this issue promptly to prevent engine overheating and further damage.