Fig. 9.1. Location of brake system components (hatchback, Station Wagon and Van models)
1. Assembling the vacuum booster of the master cylinder; 2. Brake pipe; 3. Hose; 4. Brake pipe; 5. Brake pipe; 6. Brake pipe; 7. Bracket; a. Bracket; 9. Hose; 10. Brake pipe; 11. Brake pipe; 12. Plastic tie; 13. Spring clamp.
Fig. 9.2. Master cylinder (early models) and its feed tank in section
Fig. 9.3. Sectional view of the vacuum booster unit
1. Non-return check valve; 2. Hose; 3. Hose coupling; 4. O-ring seal; 5. Washer; 6. Compaction; 7. Rubber cover.
The hydraulic brake system is equipped with a booster and is divided into two independent circuits. Each circuit controls one of the front and diagonally opposite rear brake units. The front brakes are disc brakes, the rear ones are drum brakes. The master cylinder and the vacuum booster unit to which it is attached are located on the left side of the bulkhead in the engine compartment.
The master cylinder is of the tandem type, connected to it by a system of metal tubes and hoses. The primary circuit controls the right front and left rear brakes, and the secondary circuit controls the left front and right rear brakes, respectively. Under normal circumstances, both circuits work in unison. In the event of failure of one of the circuits, braking will still be carried out effectively, although at the expense of only two wheels. At the same time, the pedal travel will increase.
The amount of hydraulic pressure in the rear brakes is controlled by pressure regulating valves, which helps prevent the rear wheels from locking up under heavy braking. Pickup models have a load-sensitive valve, linked by a spring to the rear torsion beam, which regulates the pressure according to the vehicle load. All other models use pressure-sensitive valves mounted in the master cylinder (one in each circuit). Please note that the pressure sensitive valves on Estate and Van models operate at a higher pressure than those used on Hatchback models, meaning each specific model must be fitted with the same type of valves for the correct model.
The handbrake operates the rear brakes via a lever assembly and cables that run to the backplates of each drum brake.
The instrument panel of the models described has a brake fluid level warning lamp, the circuit of which is closed by a float-type sensor installed in the filler cap of the master cylinder reservoir so that the lamp lights up whenever the fluid level drops to a dangerously low mark. In addition, these models are equipped with a handbrake application warning lamp, activated by a plunger switch installed in the base of the handbrake lever.
(Data Copied from the portal SkodaBook.ru)
The vacuum booster unit uses the vacuum in the intake manifold (it only occurs when the engine is running), to reduce the effort required from the driver to fully depress the brake pedal. The unit transmits this combined braking force to the master cylinder pistons via a push rod connected via a rod to the brake pedal. The main component of the booster is a sealed metal chamber divided into two halves by a diaphragm, the bypass channels of the chamber compartments are opened by the push rod. Under normal operating conditions, the pressure in both compartments is less than atmospheric, but when the brake pedal is applied, the bypass valve of the rear compartment opens and the pressure in it is equal to atmospheric. The resulting pressure difference forces the diaphragm, and with it the rod of the primary piston of the master cylinder, to move forward, transmitting the braking force to the master cylinder.
The front brake calipers have a single piston sliding type, under the action of which the caliper slides in a mounting bracket rigidly attached to the steering knuckle. Braking efficiency depends on this ability to slide in the mounting bracket, as well as on the condition of the pads, the walls of the caliper bore, the piston and the seals.
The rear brakes consist of a cast iron drum attached to the hub and wheel, as well as a support shield, which is mounted on the trailing arm of the rear suspension and carries the shoes and the working brake cylinder. The gap between the shoes and the drum is adjusted automatically, compensating for wear of the shoe linings.
Note: When servicing any part of the system, work carefully and methodically and maintain scrupulous cleanliness. Replace the component (together with its pair installed on the opposite side of the car), if there is any doubt about its condition. Use only genuine Skoda parts or at least good quality parts. Take note of the Warnings regarding the qualities of asbestos dust and brake fluid given in this Section. Although many companies produce brake pads with asbestos-free linings, it is safer to assume that the linings fitted to your car are not of this "harmless" type and take the precautions described above.
Note: Vehicles produced from April 1992 onwards are equipped with master cylinders with a working diameter of 22.2 mm (instead of the previously used 22.0 mm diameter cylinders) and a vacuum booster unit with a non-adjustable primary piston rod of the master cylinder; old and modified components may only be used as matched pairs. If any of them are to be replaced, select a component with the appropriate specification for this purpose.