Brake System Functions

The car is equipped with two independent brake systems:
- Hydraulic brake system with ABS.
- Handbrake system (the illustration shows the 2-cable system).

Brake Fluid Reservoir




The brake fluid reservoir is divided into two chambers:
1. A chamber for supplying the front left wheel and rear right wheel (primary circuit)
2. A chamber for supplying the front right wheel and rear left wheel (secondary circuit).
- A chamber for supplying the connection cylinder on cars with Sensonic.
- A fluid level indicator is incorporated into the cap of the brake fluid reservoir. This consists of a float and two contact pins. When the brake fluid level is low, the float sinks causing the switch contacts to make and activate the brake warning light (this happens when the level has sunk to approximate. a third from full level).
- At ignition the lamp is grounded by the generator, activating the lamp. When the engine starts and the generator begins to charge, the lamp goes off, if the brake fluid level is correct. This way the warning lamp is checked every time the ignition key is turned.

Brake Servo Unit





Purpose

The brake servo unit reinforces the driver pedal effort when the brakes are applied. The reinforcement of the applied force achieved through the servo unit is obtained from the vacuum in the engine intake manifold and amounts to around 3.9:1. The servo unit is connected to the intake manifold by a hose. The servo unit consists of a metal reservoir installed between the brake pedal and the master cylinder and connected to these by push rods. In the event of a leak in the servo unit, the two pushrods act as a single pushrod. The brakes then operate without servo assistance, with the result that a considerably greater pedal effort is required.





Brake Off
In the brakes off position the air duct (4) is closed and the vacuum chamber (7) is connected to the working chamber (6) via the open cross over valve. Equal vacuum exists on both sides of the diaphragm (1) in the brake off position.





Brake Applied
As the brake pedal is depressed the pushrod forces the valve piston and the diaphragm (1) forwards, causing the vacuum passage to close. When the push rod is pressed further, the valve piston opens a passage (4), which makes it possible for air at atmospheric pressure (5) to flow through the filter and in behind the diaphragm. As vacuum from the intake manifold acts in front of the diaphragm, the pressure difference causes the diaphragm (1) and the pushrod to the master cylinder to be moved forwards, resulting in reinforcement of the pedal force. When the pedal force ceases, the vacuum valve opens and air at atmospheric pressure on the back of the diaphragm flows across to the front and from there through the non-return valve (9) to the intake manifold. The opening for atmospheric air is closed and the return spring presses the diaphragm, valve piston and pushrod from the brake pedal back to the brake off position. The non-return valve prevents air at atmospheric pressure from flowing back from the intake manifold to the servo unit. The non-return valves only opens when the vacuum in the intake manifold is greater than in the servo unit.

Master Cylinder




Basic Description
The master cylinder consists of a tandem cylinder that is made of steel.

As the car as two independent brake circuits, it has a master cylinder with two independent pressure chambers. The master cylinder therefore incorporates two pistons: a primary piston (next to the brake pedal) and a secondary piston and also return springs for these. The secondary piston has a steel center valve that opens the ducts to the brake fluid reservoir in the brake off position.

Two pipes run from the master cylinder (primary/secondary) to the ABS unit (valve lock) that in turn supplies the wheel cylinders with brake fluid. Brake fluid reservoir is installed directly to the master cylinder.

Functions





With Brakes Off
In the brake off position the return springs press the pistons against the rear end position. In this position both return ducts are open and the brake system remains unpressurized. Backward movement is limited by a stop pin.





With Brakes Applied (Both Circuits In Operation)
When the brake pedal is pressed down, the primary piston is pushed forwards by the pushrod.

The return duct to the brake fluid reservoir is closed and the pressure in front of the primary piston increases. The pressure also affects the secondary piston which is pushed forwards with the result that the secondary piston return duct is closed by the central valve. The hydraulic pressure in both brake circuits increases, end: because the pistons are the same size, the pressures in both brake circuits are the same. The pressure is transmitted in the brake system and affects the brake piston in each brake housing. The brake pistons force the brake blocks against the brake discs.

When the brake pedal is released, the pistons in the master cylinder return and open the return ducts. The pressure ceases and the brake pistons in each brake





With Brakes Applied (One Circuit Out of Operation)
When the brake pedal is depressed and there is for example a leak in the primary circuit, the primary piston is pressed forwards by the push rod until it mechanically affects the secondary piston. The secondary piston closes the return passage with the central valve and hydraulic pressure is built up in the secondary circuit only.

If there is a leak in the secondary circuit the secondary piston is pushed forwards and will touch bottom in the master cylinder. In both cases a longer pedal movement is required to accomplish the desired braking action.

Brake Caliper-Front





Each brake caliper consists of a hydraulic body with a brake piston and two brake pads and also a bracket.

The front hydraulic body is mobile and slides over two guide pins installed on the bracket. the guide pins are stainless steel and should not be lubricated.

The hydraulic body has a piston with two grooves that give lesser contact surfaces to the brake bads and greater cooling for the piston. this design gives a little heat distribution to the brake fluid. the brakes can therefore tolerate a high thermal load. It is important that the brake piston is installed in the correct position after removal, so that the right cooling is achieved.

When the brake is operated the hydraulic pressure acts partly straight to the brake cylinder and partly against the brake cylinder walls. the brake piston forces the inner brake shoes against the brake disc. Meanwhile the hydraulic body slides across so that the outer brake shoes press against the brake disc. When the hydraulic pressure ceases the brake piston in each brake cylinder returns to the brake off position with the aid of the piston seal.

Brake Caliper-Rear




Each brake caliper consists of a hydraulic body divided into two halves that are held together by a screw joint. Each half is supplied with a brake cylinder. At braking both pistons press the brake pads against the brake disc. their is a groove in each piston to ensure the brake shoes do not wear unevenly. It very important that the pistons are installed correctly after removal.

When the brake pedal is released the piston seals return the pistons to the brake off position.

Handbrake system - 2 Cable Type




When the handbrake is operated, the force is transferred via two cables to the levers. One cable runs from the handbrake to the right rear wheel and the other from the handbrake to the left rear wheel. The lever forces the brake shoes against the brake drum so that braking takes place.

When the hand-brake is operated the handbrake lamp on the instrument panel comes on. When the handbrake is released, the return spring returns the levers and the brake shoes move to the brake off position.