Which component's reservoir should be known for checking the hydraulic brake fluid?

The hydraulic brake master-cylinder reservoir is crucial for checking the hydraulic brake fluid because this component stores the brake fluid needed for the braking system to function effectively. The master cylinder is responsible for generating the hydraulic pressure necessary to actuate the brake mechanisms. Regularly checking this reservoir ensures that there is sufficient fluid to maintain brake performance and safety.

Maintaining the correct fluid level in the master-cylinder reservoir is essential, as low fluid levels can lead to reduced braking efficiency, increased pedal travel, or even complete brake failure. Additionally, if the fluid is contaminated or the system has air in it, it can lead to brake system malfunctions. Therefore, familiarity with the master-cylinder reservoir is critical for anyone inspecting vehicle hydraulic brake systems.