Hydraulic System: Description and Operation
Hydraulic Brake ActuationCAUTION: Blistering or swelling of rubber brake components may indicate contamination of the brake fluid by a petroleum based substance. New rubber components must be installed in the hydraulic system if contaminated and the entire hydraulic brake system must be flushed with clean brake fluid to prevent recontamination.
The hydraulic brake actuation system consists of the following components:
^ anti-lock brake system (ABS)
^ brake master cylinder
^ front disc brake calipers
^ rear wheel cylinders (base brake system)
^ rear disc brake calipers (4-wheel disc brake system)
^ brake tubes and hoses
The hydraulic brake system is diagonally split with the LH front and RH rear brakes on one circuit and the RH front and LH rear brakes on the other circuit.
Disc/Drum Brake Actuation (Base Brake System)
The brake pedal is connected to the brake master cylinder. When the brake pedal is pressed, brake fluid is pushed through the double-walled steel lines and flexible hoses to the rear wheel cylinders and the front disc brake calipers. The brake fluid enters the rear wheel cylinders, forcing the rear wheel cylinder pistons outward against the brake shoes and linings. The brake shoes and linings press against the braking surfaces of the brake drums. The front disc brake caliper pistons are forced outward against the brake pads and linings, and contact the braking surfaces of the front disc brake rotors. When the brake pedal is released, the pressure is relieved, returning the front disc brake caliper pistons and rear wheel cylinder pistons and the brake shoes, brake pads and linings to the unapplied position.
Disc/Disc Brake Actuation (4-wheel Disc Brake System)
The brake pedal is connected to the brake master cylinder. When the brake pedal is pressed, brake fluid is pushed through the double-walled steel lines and flexible hoses to the rear disc brake calipers and the front disc brake calipers. The brake fluid enters the disc brake calipers, forcing the caliper pistons outward. The rear disc brake caliper pistons are forced outward against the brake pads and linings, and contact the braking surfaces of the rear disc brake rotors. The front disc brake caliper pistons are forced outward against the brake pads and linings, and contact the braking surfaces of the front disc brake rotors. When the brake pedal is released, the pressure is relieved, returning the front disc brake caliper pistons, rear disc brake caliper pistons, and the brake pads and linings to the unapplied position.
Brake Fluid
WARNING: Brake fluid contains polyglycol ethers and polyglycols. Avoid contact with eyes. Wash hands thoroughly after handling. If brake fluid contacts eyes, flush with running water for 15 minutes. Get medical attention if irritation persists. If taken internally, drink water and induce vomiting. Get medical attention immediately. Failure to follow these instructions may result in personal injury.
^ Do not reuse brake fluid drained or bled from the brake system.
^ Do not use brake fluid that has been stored in an open container.
^ Do not mix different types of brake fluid.
Brake Master Cylinder
The brake master cylinder is a dual-piston type. The brake master cylinder operates as follows:
^ When the brake pedal is pressed, pressure is applied by a mechanical linkage to the primary and secondary pistons.
^ Brake master cylinder pistons apply hydraulic pressure to the 2 hydraulic circuits.
The brake master cylinder consists of the following components:
^ brake master cylinder reservoir
^ brake master cylinder body
^ primary piston
^ secondary piston snap ring
Whenever the brake master cylinder is removed from the brake booster, new nuts must be installed.
Brake Fluid Level Warning Switch
The brake fluid level warning switch is an integral part of the brake master cylinder reservoir. It consists of a float containing a magnet and a reed switch mounted in the bottom of the brake master cylinder reservoir.
When the brake fluid in the brake master cylinder reservoir gets to a predetermined level, the float and magnet actuate the reed switch, causing the red brake warning indicator to illuminate. Loss of brake fluid from either the primary (front) or secondary (rear) system will cause this system to activate. If the brake fluid level warning switch is inoperative, a new brake master cylinder reservoir must be installed.
Brake Master Cylinder Reservoir
NOTE: Whenever the brake master cylinder reservoir is removed from the brake master cylinder, new seals must be installed.
The brake master cylinder reservoir:
^ is mounted to the brake master cylinder.
^ holds the fluid supply for each brake master cylinder hydraulic piston.
^ provides visual fluid level markings.
^ contains the brake master cylinder fluid level warning switch.
On vehicles equipped with a manual transmission, the reservoir is shared with the clutch master cylinder.
Brake Lines and Hoses
CAUTION: Never use copper tubing. It is subject to fatigue, cracking and corrosion, which could result in brake tube failure.
Steel tubing is used throughout the brake hydraulic system. All brake tube fittings must be correctly double-flared to provide strong, leakproof connections.
If a section of brake tube is damaged, the entire section must be removed and a new tube of the same type, size, shape and length installed.
When installing new hydraulic brake lines, hoses, or connectors, tighten all connections securely. After installation, bleed the brake system.