Brakes and Traction Control: Description and Operation

HYDRAULIC BRAKE ACTUATION

Caution:
^ 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:
^ if equipped, anti-lock brake system (ABS)
^ brake master cylinder
^ brake pressure control valve (without ABS)
^ disc brake calipers
^ rear wheel cylinders
^ 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 Actuation
The brake pedal is connected to the brake master cylinder. When the brake pedal is depressed, brake fluid is pushed through the double-walled steel lines and flexible hoses to the rear wheel cylinders and the front disc brake caliper. The brake fluid enters the rear wheel cylinder, forcing the rear wheel cylinder pistons outward against the brake shoe and lining. The brake shoe and lining press against the braking surface of the brake drum. The front disc brake caliper pistons are forced outward against the brake pad and lining, and contact the braking surface of the front disc brake rotor. 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 shoe, brake pad and lining 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 depressed, pressure is applied by mechanical linkage to the primary and secondary piston.
^ Brake master cylinder pistons apply hydraulic pressure to the two hydraulic circuits.
The brake master cylinder consists of the following components:
^ brake master cylinder degas bottle
^ brake master cylinder body
^ primary piston
^ secondary piston
^ snap ring

Note:
^ 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 degas bottle. It consists of a float containing a magnet and a reed switch mounted in the bottom of the brake master cylinder degas bottle.
When the brake fluid in the brake master cylinder degas bottle gets to a predetermined level, the float and magnet actuates the reed switch that causes 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 degas bottle must be installed.

Brake Master Cylinder Reservoir

Note:
^ Whenever the brake master cylinder degas bottle is removed from the brake master cylinder, new seals must be installed.

The brake master cylinder degas bottle:
^ is mounted to the brake master cylinder.
^ holds fluid supply for each brake master cylinder hydraulic piston.
^ provides visual fluke level markings.
^ contains the brake master cylinder fluid level warning switch.
On vehicles equipped faith a manual transaxle, the degas bottle is shared with the clutch master cylinder.

Brake Pressure Control Valve
The brake pressure control valve proportions the pressure to the rear brakes.
^ When the brake pedal is applied, brake fluid pressure passes through the brake pressure control valve to the rear brake system until the valve split point is reached.
^ Above its split point, the brake pressure control valve begins to reduce the hydraulic pressure to the rear brakes, creating a balanced braking condition between the front and rear brakes.

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 fitted to provide strong leak proof 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.