What role does the metering valve play in brake systems?

The metering valve's main function in brake systems is to control the timing of brake application, particularly in vehicles equipped with disc brakes in the front and drum brakes in the rear.

When the driver presses the brake pedal, the metering valve delays the application of the rear brakes until a predetermined amount of pressure is established in the front brakes. This delay allows the front brakes to engage first, which is crucial for maintaining the vehicle's stability and preventing it from nosediving during braking. By coordinating the timing of the brake system's response, the metering valve helps to ensure that the vehicle stops in a controlled and safe manner.

The other options focus on aspects that are not the primary function of the metering valve. Controlling hydraulic pressure and regulating fluid temperatures are managed by different components within the brake system, and measuring fluid levels is typically the responsibility of a separate sensor or gauge. Thus, the correct answer highlights the specific role of the metering valve in managing brake application timing, ensuring effective and safe braking performance.