Which symptom may indicate that brake fluid needs to be changed?

The presence of dark or murky fluid in the brake system serves as a clear indicator that the brake fluid may need to be changed. Over time, brake fluid can absorb moisture and contaminants from the environment, leading to a deterioration of its fluid properties. This deterioration can compromise the hydraulic system's efficiency and the overall performance of the brakes. Dark or murky fluid suggests that it has absorbed moisture and potentially has debris or metal particles suspended in it, which can significantly reduce braking effectiveness and lead to problems such as brake fade or corrosion of brake components.

On the other hand, high fluid levels typically indicate that there may not be an issue, and bright red fluid often signifies that the fluid is still relatively new or in good condition, especially in systems using certain types of automatic transmission fluid. A solid brake pedal feel generally indicates that the brake system is functioning properly and can mean that the fluid is at a good level without air or moisture intrusion.