What must be checked for contamination before adding brake fluid?

Before adding brake fluid to the braking system, it is crucial to check the brake fluid itself for contamination. Brake fluid is hygroscopic, meaning it can absorb moisture over time, which can reduce its effectiveness and lead to corrosion within the braking system. Furthermore, contaminants such as dirt, oil, or other fluids can also compromise the hydraulic system’s performance and lead to potential failure. The presence of such contaminants necessitates a thorough inspection of the existing brake fluid to ensure that only clean fluid is added to maintain optimal braking performance and system integrity.

Other components like the brake pads, hydraulic lines, and brake booster certainly play important roles in the overall braking system, but they do not directly pertain to the integrity and cleanliness of the brake fluid itself, which is essential for effective braking operation.