What part controls the fluid flow through the brake system?

The spool valve is crucial in regulating fluid flow through the brake system. It functions as a hydraulic controller, allowing the brake fluid to flow when needed and preventing flow when brakes are not applied. This is essential for maintaining the effectiveness of the braking system, as it ensures that hydraulic pressure is applied precisely when the driver presses the brake pedal, leading to the desired braking force. The spool valve achieves this by opening or closing passages within the hydraulic system, thus controlling the pressure and flow direction of the brake fluid.

Understanding its operation is vital for diagnosing brake system issues, as a malfunctioning spool valve can lead to inadequate braking response or system leaks. The other components mentioned, while important in their roles, do not directly manage the flow of fluid in the same manner as the spool valve. Therefore, identifying the spool valve as the controller of fluid flow highlights its critical role in the overall functionality of the brake system.