Which fluid is typically checked when inspecting the hydraulic brake system?

The correct choice for inspecting the hydraulic brake system is brake fluid. Brake fluid is essential for the operation of the hydraulic brake system as it transmits force from the brake pedal to the brake components. It is critical to ensure that the brake fluid is at the proper level and in good condition, as any contamination or drop in level can lead to brake failure or diminished braking performance.

The hydraulic system relies on the incompressibility of the brake fluid to function effectively, meaning that without an adequate amount of fluid, or if the fluids are contaminated, the brakes could become less responsive or fail entirely. Regular checks of brake fluid levels and quality are a key part of vehicle maintenance and safety protocols for automotive technicians.

On the other hand, transmission fluid, power steering fluid, and coolant serve specific functions unrelated to the braking mechanism and are not involved in the hydraulic processes of the brake system.