Mercedes C-Class

W203 since 2000 of release

Repair and operation of the car



Mercedes-Benz
+ Mercedes-Benz cars of class C (W-203)
+ Operation manual
+ Routine maintenance
+ Engine
+ Cooling system and heating
+ Power supply system and release
+ Engine electric equipment
+ Manual transmission
+ Automatic transmission
+ Coupling and power shafts
- Brake system
   Specifications
   Replacement of blocks of a forward disk brake
   Removal and installation of a forward support
   Replacement of back brake shoes
   Removal and installation of a back support
   Removal and installation of a brake disk
   Check of a brake disk
   Dual main brake cylinder
   Replacement of brake shoes of the parking brake
   Removal and installation of a cable of the drive of the parking brake
   Removal and installation of the switch of a stoplight
   Removal of air from the brake system
   Removal and installation of a brake hose
   Check of the amplifier of a brake
+ Suspension bracket and steering
+ Body
+ Onboard electric equipment







Brake system

Main data

Hydraulic elements brake and auxiliary BAS and ESP systems

1 — Double-circuit GTTs
5a — the Support of the brake mechanism of the right forward wheel
5b — the Support of the brake mechanism of the left forward wheel
6a — the Support of the brake mechanism of the right back wheel
6b — the Support of the brake mechanism of the left back wheel
A7/7 — the Amplifier of emergency brake application (BAS)
b1 — BAS diaphragm course Sensor
s1 — BAS otpuskaniye Sensor switch
y1 — the Electromagnetic BAS valve
N47-5 — the ESP/BAS Control unit
S11 — the Sensor switch of level of brake fluid

Scheme of a hydraulic contour of the antistrange ESP system

7 — the Control valve
9 — the Odnokhodovy control valve of the returnable pump
11 — the Low pressure accumulator
12 — the Damper with the operating plate
13 — the Diaphragm of a quencher of pulsations
14 — Barochuvstvitelnaya the operating plate
A7/3 — Gidromodulyator of auxiliary brake systems
m1 — the Pressure head and returnable pump
p1 — the Self-filled pump of a forward contour
p2 — the Self-filled pump of a back contour
y6 — the Left forward electromagnetic valve, maintenance of pressure
y7 — the Left forward electromagnetic valve, dumping of pressure
y8 — the Right forward electromagnetic valve, maintenance of pressure
y9 — the Right forward electromagnetic valve, dumping of pressure
y10 — the Left back electromagnetic valve, maintenance of pressure
y11 — the Left back electromagnetic valve, dumping of pressure
y12 — the Right back electromagnetic valve, maintenance of pressure
y13 — the Right back electromagnetic valve, dumping of pressure
y18 — the Operating electromagnetic valve of a forward contour
y19 — the Operating electromagnetic valve of a back contour
y22 — the Soaking-up electromagnetic valve of a forward contour
y23 — the Soaking-up electromagnetic valve of a back contour
B34 — the Sensor of brake pressure of ESP (model, release with 08/01)
B34/1 — the Sensor of 1 pressure of ESP (is not established on models 08/01)
B34/2 — the Sensor 2 pressure of ESP (is not established on models 08/01)
VA — the Contour of a forward axis
HA — the Contour of a back axis
VL — the Brake of a forward left wheel
VR — the Brake of a forward right wheel
HL — the Brake of a back left wheel
HR — the Brake of a back right wheel

Electric elements of management brake and auxiliary BAS and ESP systems

A1 — the Control panel
e7 — the Control lamp of level of brake fluid and raising of the parking brake
e17 — the Control lamp of ABS
e41 — the Control lamp of ESP
p13 — the Multipurpose display
A7/3 — Gidromodulyator of auxiliary brake systems
A7/7 — the Amplifier of emergency brake application (BAS)
b1 — BAS diaphragm course Sensor
s1 — BAS otpuskaniye Sensor switch
y1 — the Electromagnetic BAS valve
B24/2 — the Sensor of cross overloads
B34/1 — the Sensor of 1 brake pressure of ESP
B34/2 — the Sensor 2 of brake pressure of ESP
L6/1 — the RPM meter of the left forward wheel
L6/2 — the RPM meter of the right forward wheel
L6/3 — the RPM meter of the left back wheel
L6/4 — the RPM meter of the right back wheel
N10/1 — the Forward SAM control unit with a box of safety locks and the relay
N10/2 — the SAM Control unit with a back box of safety locks and the relay
N47-5 — the ESP/BAS Control unit
N49 — the Sensor of an angle of rotation
N64 — the Sensor of intensity of roving
N72/1 — the Control unit of the top control panel
s1 — the Sensor switch of shutdown ESP (ESP OFF)
S9/1 — the Sensor switch of stoplights
S10/1 — the Contact sensor of blocks of the brake mechanism of the left forward wheel
S10/2 — the Contact sensor of blocks of the brake mechanism of the right forward wheel
S10/3 — the Contact sensor of blocks of the brake mechanism of the left back wheel
S10/4 — the Contact sensor of blocks of the brake mechanism of the right back wheel
S11 — the Sensor switch of level of brake fluid
S12 — the Sensor switch of raising of the parking brake

Design of the capacitor sensor of turn and acceleration of a body of the ESP system

and — the Silicon ring
b — the Spring crossing point
with — the Electronic sensor

Arrangement of the sensor of turn and acceleration of a body of the antistrange ESP system

Functioning of the capacitor sensor of the steepness of turn and acceleration of a body of the ESP system


The hydraulic brake system consists of the main brake cylinder, the amplifier of a brake, the ABS block and disk brakes of forward and back wheels. The hydraulic brake system is divided into two contours. One contour influences brakes of lobbies, the second contour – back wheels. At refusal of one of contours, for example, owing to liquid leak, braking of the car is carried out by other contour. Liquid pressure in both contours is created by the doubled main brake cylinder operating from a brake pedal.

The tank with brake fluid is in a motive compartment, from the driver under a cover over the main brake cylinder. It supplies with brake fluid all system. Liquid volume in the tank has to be controlled constantly.

The description of work of systems of anti-blocking of brakes of ABS, the amplifier of emergency brake application of BAS and the electronic program of stabilization of stability (antistrange system) is provided in the section "Governing Bodies and Methods of Safe Operation".

Forward brakes have a support with a floating bracket. Such design for the drive of both brake shoes demands only one piston. Back brakes have a motionless support.

The amplifier of a brake accumulates a part of the vacuum created in the soaked-up engine pipeline. As the diesel engine has no necessary vacuum on absorption, cars with the diesel engine have the special vacuum pump installed ahead on a head of cylinders, and is set in motion from the camshaft.

By means of the corresponding valve, the effort from a pedal of a brake increases under the influence of vacuum.

The foot parking brake affects through cables brakes of back wheels. On back wheels the drum brakes which are built in disk brakes are in addition established. Drum brakes are put in action only from a pedal of the parking brake. Brake shoes of back wheels are established automatically that demands only in rare instances of adjustment of the parking brake, for example, after carrying out repair.

Features of the auxiliary ABS, ESP and BAS systems

Functioning of a hydraulic contour of auxiliary brake systems
Components of systems of the closed contour of dynamic control of the ABS, ASR and ESP systems are a part of the hydromodulator of auxiliary brake systems (A7/3).

Pressure head and returnable pump (A7/3m1)

The self-filled pressure head and returnable pumps (p1, p2) are built in assembly of the hydromodulator (A7/3) and are switched by pulse signals in phases of forcing and dumping of pressure of system of active management of ASR and ESP, and also during adjustment of a returnable stream at ABS activation.

Electromagnetic valves of maintenance and dumping of pressure (A7/3y6-y13)
One 2/2-hodovy valve is used at management of pressure in contours of each of wheels in phases of forcing/deduction and deduction/dumping of the operating ABS, ASR and ESP modes.

Low pressure tank (11)

The low pressure tank (11) is filled with brake fluid in a phase of dumping of pressure of ABS, ASR or ESP and provides its transfer to pressure head returnable pump (p1/p2).

The operating electromagnetic valves of contours (A7/3y18 and y19)

Electromagnetic valves switches (y18 and y19) provide a cut-off of active pressure head contours of forward and back axes from GTTs during functioning of ASR and ESP. Also valves provide dumping of pressure at rise it over 150 atm. The brake fluid passed via valves switches goes back to GTTs.

The soaking-up electromagnetic valves (A7/3y22 and y23)

Inlet electromagnetic valves (y22, y23) open in phases of increase of pressure ASR/ESP.

Sensors of the brake pressure (B34, B34/1, B34/2)

ESP Mk20 (models to 7/01) is equipped with two sensors of brake pressure. The sensor 1 (B34/1) traces pressure in a forward brake contour, the sensor 2 (B34/2) - in back.

In ESP Mk25 (model with 8/01) only one sensor (B34) tracing pressure in a forward contour is used.

Information issued by sensors is transferred to the control unit and used at calculation of parameters of the closed contour of management.

Decrease in a noise background

The self-started pressure head and returnable pumps (p1, p2) are started as necessary for the purpose of minimization of noise level.

Various damping components (13, 14) provide further repayment of noise. Each brake contour is equipped with the separate damper (12) reducing the level of the noise made by the pump.

Sensor of the steepness of turn and acceleration of a body

The sensors tracing angular speeds and cross overloads are united in assembly of the steepness of turn and cross overloads (B24/5) that allows to save the space occupied by them. Micromechanical touch assembly will transform cross and vertical projections of angular accelerations to electric signals. Elements, various on weight, under the influence of arising during not inertial movement of the vehicle (commission of turns and accelerations) of overloads provide various extent of deformation. The special electronic converter converts the received signals and on the tire of CAN transfers them to the control unit of antiprobuksovochny and antistrange systems (N47).

Principle of functioning of the sensor

The sensitive element of the sensor is created from the micromechanical ring (a) equipped with eight spring crossing points (b) providing its movement and electromagnetic action. At rotation in assembly there are additional Coriolis forces proportional to rotation speed fixed in an electromagnetic way and after transformation in the ACIS module to a form of analog signals, given on the control unit of the control panel.

The principle of measurement of cross overloads is based on use of a spring and mass element with the capacitor detector. Working tension moves from the ESP (N47-5) control unit.

The cross loadings arising during commission of turns provide the shift of a spring and mass element from balance position at a size proportional to value of the arising overload. Any change in the provision of an element leads to change of capacity of the detector. Further the recorded deviation will be transformed to the alarm tension allowing the ESP (N47-5) control unit to make quantitative assessment of sizes of the fixed cross overloads.

The electronic control unit watches that the system, in the presence of damage (for example, break of a cable), or at undervoltage, was independently disconnected. The situation is displayed on the dashboard by fire of a control lamp of ABS of orange color. At the same time the ESP and BAS systems are at the same time disconnected that is displayed by fire of a signaling device of ESP. The main brake system keeps at the same time the working capacity. In the course of braking the car behaves as if the ABS system is absent.

If, for example, during the movement the control lamp of ESP lights up, then it indicates existence of malfunction of the amplifier of braking or antistrange system. BAS and ESP are disconnected. The usual system at the same time keeps the working capacity.

If during the movement the red control lamp lights up (a symbol: a call sign) systems of braking, it is necessary to stop and find out the reason immediately. The insufficient amount of brake fluid or the cocked parking brake can be the reasons.

If during the movement the control lamp of ABS lights up:

1. Stop the car, switch off the engine and again start it.
2. Check tension of the rechargeable battery. If tension less than 10.5 In, charge the battery.

If the control lamp of ABS lights up in a start of motion and then after a while dies away, then it indicates the low voltage of the rechargeable battery which increases after the beginning of operation of the generator.


3. Check whether plugs of the rechargeable battery are reliably fixed.
4. Put the car on supports, remove wheels and check the electric wires going to sensors of speed of wheels for existence of external damages. Other checks it is necessary to carry out HUNDRED in conditions. Electronics has self-diagnostics, the available malfunctions are registered system automatically. Check of records and elimination of malfunctions are made on HUNDRED.

Before performance of electrowelding works it is necessary to disunite the ABS socket. Connection is located in motive a compartment, above, from the driver, behind a removable cover. Connection undocks only at the switched-off ignition. When performing paint and varnish works it is not allowed to heat the control unit to temperature above +90 °C.

When cleaning the brake system dust which can do harm to health of the person therefore it is impossible to inhale brake dust is emitted.

Work with the brake system demands special purity and exact observance of instructions. In the absence of necessary experience it is expedient to address on HUNDRED.


At movement along wet roads it is necessary to press periodically a brake pedal for removal of moisture from disks of brakes.


In the course of rotation of a wheel moisture under the influence of centrifugal force is dumped from brake disks, but there is a silicone film, rubber attrition products, lubricant and other pollution reducing efficiency of brakes.

After installation of new brake shoes the last have to be earned extra. Therefore the first 200 km of a run should not be braked needlessly strongly.

The disk brakes having corrosion when braking create the effect of jolting which is not disappearing over time. In this case it is necessary to replace brake disks.

And rain flutes lead burning of dirt to a surface of brake shoes to formation of furrows on a surface of brake disks that leads to decrease in efficiency of braking.