Design

Design

Hydraulic braking system




1. Primary circuit (1)
2. Secondary circuit (2)
3. Master cylinder
4. Brake control module (BCM)
The hydraulic brake system is a two-circuit diagonal brake system.
The hydraulic brake system is divided up as follows:
The primary circuit (1) includes:
- The front chamber for the master cylinder
- Cylinder in the front left-hand brake caliper
- Cylinder in the rear right-hand brake caliper.
The secondary circuit (2) includes:
- The rear chamber for the master cylinder
- Cylinder in the front right-hand brake caliper
- Cylinder in the rear left-hand brake caliper.
Two brake pipes run from the master cylinder (3) to the brake control module (BCM) (4), where the brake pipes then branch to the wheel brakes.

Servo cylinder




1. Vacuum hose connection
2. Front push rod
3. Membrane spring
4. Rubber membrane
5. Guide housing
6. Push rod spring
7. Rear push rod
8. Air cleaner (ACL)
9. Connecting device EBA
10. Reaction disc
11. Membrane support.
The vehicle is equipped with a single servo cylinder. It has integrated mechanical brake assistance (EBA). The servo cylinder is located between the brake pedal and the master cylinder and is actuated directly by the brake pedal. It ensures that less pedal force is required when braking with the aid of vacuum from the vacuum pump and via the intake manifold for the engine. The check valve located by the vacuum pump prevents air from flowing back to the servo cylinder.

Mechanical brake assistance (EBA)




1. Connecting device.
The mechanical brake assistance (EBA) is integrated in the servo cylinder.
The connecting device (1) is designed as a single unit. It is fully integrated in the servo cylinder and only actuates the standard version of the servo cylinder in the guide housing.
The function can shorten the braking distance considerably, as it is activated when the brake pedal is depressed quickly and firmly.
In such a situation, the ability of the servo cylinder to reinforce the brake force is fully utilized.

Master cylinder




1. Push rod (part of primary piston, connected to the servo cylinder)
2. Primary circuit chamber
3. Valve
4. Secondary circuit piston
5. Secondary circuit chamber.
The master cylinder is designed for a diagonally split brake system.
One front wheel and one rear wheel are connected together in a circuit. The two chambers in the master cylinder supply one circuit each in the brake system.
The master cylinder is of the tandem type. It contains two pistons, which are connected in series. The master cylinder is actuated by the servo cylinder push rod (1) and brake fluid is pressed into the brake pipes when the brake pedal is pressed. The brake fluid, which is moved in the system, generates an increase in pressure in the wheel brakes causing the vehicle to brake.
There is a valve (3) in the bottom of both pistons. These ensure that the remaining pressure in the chambers (for example after braking using ABS) is released, so that the seals in the master cylinder are not damaged. They also ensure that new brake fluid can be added to the system in the event of wear to brake pads and disc brakes.
For safety reasons, each circuit has a specific piston for pressing the brake fluid out of the master cylinder and into the brake pipes.
Springs in the master cylinder move the pistons back to their resting position when the vehicle is not braking. In this situation the valves are open and both the chambers (brake circuits) are connected to the brake fluid reservoir.
When the brake pedal is pressed, both pistons are moved. The valves are closed and pressure can build up in the brake fluid.
The brake fluid reservoir for the master cylinder ensures that the correct amount of brake fluid is supplied in the system, irrespective of wear to brake pads and disc brakes.

Wheel brakes, general




1. Brake caliper
2. Retainer
3. Rubber bushing
4. Sliding pin
5. Brake pads
6. Brake pipe
7. Bleed nipple
8. Piston
9. Brake fluid inlet
10. Sealing ring
11. Dust boot.
The vehicle has disc brakes on all four wheels to ensure optimum braking performance. The foot brake is combined with the parking brake on the rear axle. The brake discs are ventilated on the front axle, integrated with the wheel hub. The brake discs are solid on the rear axle.
The brake caliper (1) comprises two halves joined with screws, positioned over the brake disc. The caliper grips across the disc brake and slides in the holder on two sliding pins (4). The sliding pins are greased and protected with a rubber bushing (3). The braking force from the brake pads (5) is absorbed via the holder (2), which transfers the force to the spindle.
The sliding pins are made of steel. They are screwed into the armature, which is secured to the wheel spindle.
The brake caliper contains a piston (8) together with a sealing ring (10) and dust boot (11). The piston cylinder is made of steel.
The piston presses directly on the inner brake pad against the brake discs. On account of the action-reaction principle the brake caliper (1) is pressed backwards. This movement presses the outer brake pad against the brake disc. (Also see Foot brake and parking brake) The sliding brake caliper's retainer (2) presses the outer brake pad against the brake disc.
The dust boot prevents dirt getting in between the cylinder and piston.
Old brake calipers at the rear are replaced with new calipers filled with brake fluid from the factory. This simplifies bleeding.
The splash guard prevents water and salt from soiling the brake disc. Any soiling results in reduced friction and hence reduced braking power.

Parking brake




1. Control lever
2. Bracket
3. Primary mechanical cable
4. Adjuster nut
5. Compensator
6. Secondary mechanical cables.




The control lever (1), in the picture above, applies to model years up to and including 2007. The control lever, in the picture to the left, applies to model year 2008 -.
The rear brake caliper has an integrated parking brake mechanism.
The mechanism is self-adjusting. Adjustment takes place every time after braking.
The control lever (1) is located between the front seats. The control lever contains a locking arrangement. This is released with the push-button in the lever handle. The control lever is mounted on a shaft. The shaft is mounted in a bracket (2) which is screwed to the tunnel.
On the front end of the primary mechanical cable (3) is an adjuster nut (4) for manual adjustment of the cables. The primary mechanical cable is routed through a hole in the front floor to the compensator (5), where the two secondary mechanical cables (6) are mounted. The secondary mechanical cables are routed crosswise to the relevant brake caliper.
The secondary mechanical cables are routed on the underside of the floor to the cross member under the rear seat, where they are secured in two clamps on either side. They are then routed via a mechanical cable holder in the floor to a clamp in the control arm. The mechanical cable bushing is mounted in the caliper and the end of the cable is mounted in the caliper lever.