* Incompatible Fluids: Brake fluid and coolant (the fluid in your radiator) are chemically incompatible. They will react, potentially causing a violent reaction that could damage your cooling system.
* Corrosion: Brake fluid is extremely corrosive to many metals commonly found in your engine's cooling system, including aluminum. This will lead to rapid corrosion and potential leaks in your radiator, hoses, and engine block.
* Sealing Failure: Brake fluid can attack and degrade the seals and gaskets within your cooling system, leading to leaks and further damage.
* Reduced Cooling Efficiency: The mixture of brake fluid and coolant will drastically reduce the coolant's ability to absorb and dissipate heat, leading to engine overheating and potential catastrophic engine failure.
* Toxicity: Brake fluid is toxic and harmful if ingested or if it comes into contact with skin. A leak could lead to environmental contamination.
In short, mixing brake fluid and coolant will likely cause significant and expensive damage to your vehicle's cooling system. If you accidentally put brake fluid in your overflow tank, immediately drain the entire cooling system and thoroughly flush it with clean water and then refill it with the proper coolant. It's best to have a professional mechanic do this to ensure all components are properly inspected and cleaned.
