What might cause brake fluid to appear contaminated?

Moisture absorption over time is fundamental to understanding why brake fluid can appear contaminated. Brake fluid is hygroscopic, meaning it has the ability to absorb water from the atmosphere. As this moisture accumulates, it not only alters the chemical composition of the brake fluid but can also lead to a decrease in its boiling point. This change in properties can result in brake performance issues, such as brake fade, especially under high-temperature conditions.

Moreover, the presence of water in the brake fluid can lead to corrosion within the brake system components, including the master cylinder and brake calipers, further promoting contamination. Regular inspections are vital to monitor for this issue, but regardless of maintenance, moisture absorption is a systemic problem that affects all brake systems exposed to air over time. This is why the option regarding moisture absorption is accurate in identifying a primary cause of contaminated brake fluid.