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Question

Difficulty: MediumBraking Systems

Automotive hydraulic braking systems incorporate specialized valves within the hydraulic circuit to balance pressure distribution and ensure safe operation. Match each brake valve on the left with its primary function on the right.

  • Metering valveDelays hydraulic pressure to the front disc brakes until the rear drum shoes overcome return spring tension
  • Proportioning valveRestricts hydraulic pressure delivered to the rear brakes under heavy braking to prevent rear-wheel skidding
  • Pressure differential valveShifts a central piston to trigger the instrument cluster brake warning light when fluid pressure is lost in one hydraulic circuit
  • Residual pressure check valveMaintains slight positive line pressure in drum brake circuits to prevent air from bypassing the wheel cylinder cup seals

Answer

Metering valve matches with delaying front disc application; Proportioning valve matches with restricting rear hydraulic pressure under hard braking; Pressure differential valve matches with triggering the dashboard warning light on hydraulic failure; Residual pressure check valve matches with maintaining slight positive pressure to seal wheel cylinder cups.
Each hydraulic valve performs a distinct regulatory or safety function within the braking system: the metering valve synchronizes front and rear brake application timing, the proportioning valve controls rear brake pressure under forward weight transfer, the pressure differential valve senses line pressure loss to alert the driver, and the residual check valve keeps drum wheel cylinder cup seals expanded.

Step-by-Step Solution

1
Identify the valve responsible for balancing front-to-rear timing differences in disc/drum combination systems.
The metering valve delays front disc caliper pressure until rear drum shoes overcome return springs.
Disc brakes engage almost instantly, whereas drum shoes require hydraulic force to overcome mechanical return spring tension.
2
Identify the valve that prevents rear axle lockup during aggressive deceleration.
The proportioning valve limits rear hydraulic pressure rise.
Weight shifts forward during braking, unloading the rear tires and making them prone to early lockup if full hydraulic pressure were applied.
3
Identify the diagnostic safety switch that detects hydraulic circuit failure.
The pressure differential valve slides a central piston to ground the brake warning light circuit.
A leak in one split hydraulic circuit causes a pressure drop, pushing the piston toward the low-pressure side.
4
Identify the valve that keeps drum brake hydraulic seals seated at rest.
The residual pressure check valve keeps slight constant pressure in drum lines.
Maintaining 2 to 10 psi prevents atmospheric air from being sucked past wheel cylinder cup seals into the hydraulic fluid.

Key Concept

Hydraulic Brake Control and Warning Valves
Estimated Time:1m 0s
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Topics

Braking Systems

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