Hydraulic Brake System Description and Operation

Hydraulic Brake System Description and Operation

Conventional Brakes
Saturn models have an Antilock Brake System (ABS), equipped with front and rear disc brakes and power assist. This information concerns itself with the conventional brake system.

The following descriptions explain the operation of the components used on the conventional brake system.

Master Cylinder
The master cylinder is a dual circuit unit designed for use in diagonally split hydraulic systems. With a diagonally split system, the left front and right rear brake are on one hydraulic circuit, while the right front and left rear are on the other.

A brake fluid level switch, located in the brake fluid reservoir (attached to the master cylinder), is also provided. The switch will activate the RED BRAKE telltale lamp (located on instrument panel) should the brake fluid level become low. After the brake fluid level is corrected and a moderately high brake pedal force is applied, the RED BRAKE telltale lamp should go Off.

Vacuum Booster
The vacuum booster is a single diaphragm vacuum suspended unit. Engine vacuum is provided to vacuum booster through a hose and a vacuum check valve. The one-way check valve is provided between engine and the booster to prevent a loss of booster vacuum when engine vacuum falls below that stored in booster. When brakes are not applied, internal valves within the booster provide vacuum to both sides of diaphragm. When brakes are applied, air at atmospheric pressure is applied to one side of the diaphragm. Since a higher pressure now exists on one side of diaphragm than the other, a force is created, assisting brake application.

Front Caliper
Front calipers are single piston, sliding caliper units. They are fastened to the caliper support with two bolts. Brake pressure, created in the master cylinder, acts equally on the caliper piston and caliper body (in the bottom of the caliper bore). This causes the piston to move outward (pushing inboard brake pad against the brake rotor) and caliper body to slide inward (pushing outboard brake pad against brake rotor), creating stopping force. The front calipers are serviceable to the extent that they can be disassembled, cleaned, and fitted with new seals. However, since the piston bore cannot be honed, if extensive bore damage is present, the caliper body must be replaced.

Rear Caliper
Rear calipers are dual piston, fixed caliper units. They are fastened to the knuckle with two bolts. Brake pressure, created in the master cylinder, acts equally on the caliper pistons. This causes the pistons to move outward (pushing the inboard and outboard brake pads against the rotor), creating stopping force. The rear calipers are serviceable to the extent that they can be disassembled, cleaned, and fitted with new seals. However, since the piston bore cannot be honed, if extensive bore damage is present, the caliper body must be replaced.