The Dust Boot protects the caliper seal, caliper piston slide surface, and internal caliper parts. If damaged, excessive caliper-seal wear results, causing fluid leakage and damaging delicate internal parts. Damaged dust boots require caliper service. These keep the caliper in place and retract the caliper. Damaged hardware cause excessive pad wear, dragging and brake noise, and should be replaced.
Old fluid contains particles which can plug and corrode the brake lines.
On some model vehicles, a Metering Valve may be installed to balance the pressure between the front disc brakes and rear drum brakes on vehicles with front disc brakes. On some model vehicles, a Proportioning Valve may be used to reduce the hydraulic force applied to rear drum brakes during rapid braking, preventing rear wheel locking and skidding. A Warning Sensor turns the brake warning light on during a hydraulic brake malfunction. If not working, this switch should be serviced or replaced. Damaged lines should be replaced.