Mercedes C-Class

W203 since 2000 of release

Repair and car operation



Mercedes-Benz
+ Mercedes-Benz Cars of a class C (W-203)
+ Operation manual
+ Routine maintenance
+ Engine
+ cooling and heating Systems
+ 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 a drive of the parking brake
   Removal and installation of the switch of a stoplight
   Air removal from 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 systems BAS and ESP

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 braking (BAS)
b1 — the Sensor of a course of a diaphragm of BAS
s1 — the Sensor switch of an otpuskaniye of BAS
y1 — the Electromagnetic BAS valve
N47-5 — the ESP/BAS Control unit
S11 — the Sensor switch of level of brake liquid

Scheme of a hydraulic contour of protivozanosny system ESP

7 — the Control valve
9 — Odnokhodovy the control valve of the returnable pump
11 — the Low-pressure head accumulator
12 — the Damper with operating plate
13 — the Diaphragm of a quencher of pulsations
14 — Barochuvstvitelnaya an operating plate
A7/3 — Gidromodulyator of auxiliary brake systems
m1 — the Pressure head and returnable pump
p1 — the being self-filled pump of a forward contour
p2 — the being self-filled pump of a back contour
y6 — the Left forward electromagnetic valve, pressure maintenance
y7 — the Left forward electromagnetic valve, pressure dumping
y8 — the Right forward electromagnetic valve, pressure maintenance
y9 — the Right forward electromagnetic valve, pressure dumping
y10 — the Left back electromagnetic valve, pressure maintenance
y11 — the Left back electromagnetic valve, pressure dumping
y12 — the Right back electromagnetic valve, pressure maintenance
y13 — the Right back electromagnetic valve, pressure dumping
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 (it is not established on models 08/01)
B34/2 — the Sensor of 2 pressure of ESP (it 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 systems BAS and ESP

A1 — the Control panel
e7 — the Control lamp of level of brake liquid 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 braking (BAS)
b1 — the Sensor of a course of a diaphragm of BAS
s1 — the Sensor switch of an otpuskaniye of BAS
y1 — the Electromagnetic BAS valve
B24/2 — the Sensor of cross-section overloads
B34/1 — the Sensor of 1 brake pressure of ESP
B34/2 — the Sensor 2 of brake pressure of ESP
L6/1 — the Sensor of turns of the left forward wheel
L6/2 — the Sensor of turns of the right forward wheel
L6/3 — the Sensor of turns of the left back wheel
L6/4 — the Sensor of turns 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 of 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 liquid
S12 — the Sensor switch of raising of the parking brake

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

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

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

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


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

The tank with brake liquid is in an impellent compartment, from the driver under a cover over the main brake cylinder. It supplies with brake liquid all system. The liquid volume in the tank should be supervised constantly.

The description of work of systems of anti-blocking of brakes of ABS, the amplifier of emergency braking of BAS and the electronic program of stabilization of stability (Protivozanosny system) is provided in the section «Governing bodies and receptions of safe operation».

Forward brakes have a support with a floating bracket. Such design for a 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 pipeline of the engine. As the diesel engine has no necessary vacuum on absorption, cars with the diesel engine have the special vacuum pump established ahead, on a head of cylinders, and is actuated from a 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-type brakes which have been built in disk brakes are in addition established. Drum-type 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 adjustment of the parking brake, for example, after carrying out repair.

Features of auxiliary systems ABS, ESP and BAS

Functioning of a hydraulic contour of auxiliary brake systems
The structure of the hydromodulator of auxiliary brake systems (A7/3) includes components of systems of the closed contour of dynamic control of ABS, ASR and ESP systems.

Pressure head and returnable pump (A7/3m1)

Being 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 head tank (11)

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

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

Electromagnetic valves switches (and y19) provide with y18 an otsechka of active pressure head contours of forward and back axes from GTTs during ASR and ESP functioning. Also valves provide pressure dumping when lifting it over 150 atm. Brake liquid passed through valves switches goes back to GTTs.

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

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

Sensors of 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

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

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

Sensor of a steepness of turn and body acceleration

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

Principle of functioning of the sensor

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

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

Arising during commission of turns cross-section loadings provide shift of a spring and mass element from position of balance on the 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 fixed deviation will be transformed to the alarm tension allowing the ESP control unit (N47-5) to make a quantitative assessment of sizes of fixed cross-section overloads.

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

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

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

If during 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 storage 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, it indicates a low voltage of the storage battery which raises after the beginning of operation of the generator.


3. Check, whether plugs of the storage battery are reliably fixed.
4. Put the car on supports, remove wheels and check the electric wires going to sensors of number of turns of wheels on existence of external damages. Other checks it is necessary to carry out HUNDRED in conditions. Electronics has the self-diagnostics, 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 impellent a compartment, above, from the driver, behind a demountable cover. Connection undocks only at the switched-off ignition. At performance of paint and varnish works it is not allowed to heat up the control unit to temperature above +90°С.

When cleaning brake system the dust is allocated, which can harm health of the person therefore to inhale a brake dust it is impossible.

Work with 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 on wet roads it is necessary to press periodically a brake pedal for moisture removal from disks of brakes.


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

After installation of new brake shoes the last should be earned extra. Therefore the first 200 km of run it is not necessary to brake strongly needlessly.

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.

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