12. Brake system
All E28 models (with "retro" - a body) are equipped with disk forward brakes, and either drum, or disk back brakes. Lobbies and back disk brakes have the E34 models (with a modern body). Both forward, and back brakes on all models self-regulating. Some latest models are equipped with the anti-blocking brake system (ABS); it is described in the Section the General information on the anti-blocking brake system.
The hydraulic system consists of two separate contours. The main cylinder has separate tanks for each of two contours, and in case of leak of liquid or refusal of one of contours another will continue to work.
The vacuum amplifier using the vacuum and atmospheric pressure of the inlet pipeline of the engine for ensuring strengthening of hydraulic system of brakes is installed on a partition of a motive compartment.
On the E28 models the hydraulic amplifier is installed. This system uses the hydraulic pressure of the steering pump for strengthening of the brake system.
The parking brake is connected with back brakes and is put in action by a cable by means of the lever located on the central console. Assembly of the parking brake on models with back drum brakes is a self-regulating part of assembly of the back drum brake mechanism. On models with back disk brakes the parking brake works with the help of pair of brake boots located in the central part of a back brake disk and is adjusted manually.
Alarm system of wear of brake shoes
The alarm system of wear of brake shoes is connected with a red alarm lamp on an instrument guard which is lit when brake shoes wear out to the state demanding their replacement. DO NOT IGNORE this signal. If you do not replace a block shortly after this lamp lit up, brake disks will be damaged.
On some models the alarm system of wear of brake shoes also includes a lamp of a warning signal which lights up only when the brake pedal is squeezed out to warn you in advance that blocks should be replaced.
The sensor of wear fastens to brake shoes. It is located on the left forward wheel; on some models there is a sensor and on the right back wheel. The sensor of wear is a part of the closed chain. As soon as blocks wear out to the level of contact with the sensor, the disk begins to erase that part of the sensor that it is turned to a disk. Thus the wire in the sensor frays and the red lamp on an instrument guard is lit.
Always check the sensor(s) when replacing blocks. If you replace blocks before the alarm lamp lights up, the sensor(s) can remain serviceable; if the signal already lit up, the sensor should be replaced.
After completion of any procedure demanding dismantling of any part of the brake system always do trial departure to check work of brakes before normal operation of the car. You make check of brakes on a pure, dry and plain surface. Otherwise results of testing will be inexact.
Check brakes at different speeds, by easy and strong pressing a brake pedal. The car has to stop evenly, without turning in one party. Avoid blocking of brakes since it leads to sliding of wheels, reduces efficiency of braking and reduces controllability of the car.
The condition of tires, loading of the car and the angles of installation of forward wheels also influence operation of brake mechanisms.