Mercedes W124

since 1985-1995 of release

Repair and car operation



W124 Mercedes
+ Governing bodies and control devices
+ MAINTENANCE
+ 2. Maintenance (diesel engines)
+ ENGINE
+ 4. Repair of 6-cylinder petrol SOHC engines
+ 5. Repair of 6-cylinder petrol DOHC engines
+ 6. Repair of the diesel engine established in the car
+ 7. Major maintenance of engines
+ COOLING SYSTEM
+ FUEL SYSTEM
+ 10. System of injection of BOSCH CIS-E fuel (KE-JETRONIC)
+ 11. System of injection of BOSCH HFM fuel
+ 12. Fuel system of diesel engines
+ 13. Fuel system of diesel engines
+ SYSTEMS OF START, IGNITION
+ 15. System of ignition of 4-cylinder petrol engines
+ 16. System of ignition of four-cylinder petrol engines
+ PRESTARTING HEATING
+ TRANSMISSION
+ 19. Mechanical transmission
+ 20. Automatic transmission
+ POWER SHAFTS
- BRAKE SYSTEM
   22.2. General information
   22.3. Pumping of hydraulic brake system
   22.4. Brake pipelines and hoses
   + 22.5. Replacement of forward brake shoes
   22.6. Replacement of back brake shoes
   22.7. Forward brake disk
   22.8. Back brake disk
   22.9. Forward brake support
   + 22.10. Support repair
   22.11. Back brake support
   22.12. Main brake cylinder
   22.13. Vacuum amplifier of brakes
   22.14. Unilateral valve of the vacuum amplifier of brakes
   22.15. Adjustment of the parking brake
   22.16. Brake shoes of the parking brake
   22.17. Pedal of the parking brake
   22.18. Cables of the parking brake
   22.19. Stoplight switch
   22.20. Anti-blocking system (ABS)
   + 22.21. Elements of anti-blocking system
   22.22. The vacuum pump on models with diesel engines
+ SUSPENSION BRACKET
+ BODY
+ ELECTRIC EQUIPMENT
+ CHECK OF MALFUNCTIONS






22.3. Pumping of hydraulic brake system

GENERAL INFORMATION

Prevention

The brake liquid used in hydraulic system of coupling is poisonous, therefore at its hit on skin it is necessary to wash out immediately this place a plentiful quantity of water. If liquid got to eyes or in an organism, it is necessary to address immediately to the doctor. Some liquids have property easily to ignite and can light up even from contact to hot knots of the car. Besides, the liquid used in hydraulic system of coupling, dissolves paint and plastic therefore at liquid hit on a paint and varnish covering of the car wash out it a plentiful quantity of water. Also this liquid is hygroscopic, i.e. absorbs moisture from air and therefore the liquid, being stored in open ware, it is not recommended to use a long time.


Air removal from a back brake support

Pumping of hydraulic system of brakes is necessary for removal of air which considerably reduces efficiency of braking. Air can get to hydraulic system owing to system depressurization at repair, replacement of separate knots or brake liquid. To availability of air in a drive points the increased course of a pedal of a brake and its softness. Before removal of air check tightness of all knots of a drive of brakes and their connections.

Never use brake liquid repeatedly.

At performance of operation of pumping of brake system let's to level of brake liquid fall below the tank middle.

If brake liquid left system because of leak in system, find the reason and eliminate leak before further actions.

If the hydraulic system was separated partially, and the corresponding precautions were accepted to prevent further loss of liquid, it is possible to pump over only a part of system.

Pumping can be carried out with the assistant or it is independent, a set of pumping of brake system. Always act according to the instruction. It is recommended to use a set everywhere, where probably as it very much simplifies pumping procedure. If the set for pumping is not present, it is necessary to be reserved by pure capacity and a transparent plastic tube of the corresponding length which should put on densely on the pumping union. Thus the help of other person is required.

Sequence of pumping

If only partial connection of hydraulic brake system was made and the corresponding precautions were observed, it is enough to pump over only this part of system.

Carry out pumping of all system of a drive of brakes in the following sequence:

– right back wheel;
– left back wheel;
– right forward wheel;
– left forward wheel.


Prevention

On models with a control system of speed of movement (ASR) if the hydraulic system was under repair, the main brake cylinder, the hydraulic block, the hydraulic pump and the accumulator, it is also necessary to pump over the hydrosystem tank.


Pumping – the main method (two persons)

Remove a dustproof cap from the union of pumping of the wheel cylinder, clear it and dress on it the pure transparent hose which other end lower in the capacity which has been partially filled with brake liquid. The capacity should be at least on 300 mm above the pumping union. Thanks to it air hit in the cylinder through a carving of the union of pumping is prevented. Sharply press a pedal of a brake of 3-5 times with an interval of 2-3 seconds, unscrew on a turn floor the pumping union at the pressed pedal. Continuing to press a pedal, force out the liquid which was in system together with air through a hose in capacity. After the pedal will reach extreme forward situation, and the liquid effluence through a hose will stop, screw the pumping union home. Repeat these operations, the air outlet from a hose will not stop yet.

Holding a pedal in the pressed situation, screw up the pumping union against the stop and remove a hose.

Wipe the union of pumping and establish a protective cap.

Repeat these operations for other wheels.


Prevention

At air removal constantly watch availability of brake liquid in a tank, without allowing an exposure of its bottom as thus air again will get to system.


At absence the pedal should pass about a half of the course in system of brakes of air. To exclude influence of the vacuum amplifier of brakes on pumping of brakes, removal of air make at the idle engine.

Pumping – set use with the unidirectional valve

The set consists of a tube with the unidirectional valve established on it which excludes possibility of return to brake system of remote brake liquid with air vials. On some sets the transparent container in which air vials in brake liquid (see fig. are well looked through is established. Air removal from a back brake support).

Remove a dustproof cap from the union of pumping of the wheel cylinder, clear it and dress on it a hose from a set. Unscrew on a turn half the pumping union. Smoothly press a brake pedal against the stop and slowly release it in a starting position. Repeat this operation until from the union of pumping there will be no brake liquid without air vials.

Tighten the pumping union against the stop, remove from it a tube and dress a dustproof cap.


Prevention

At air removal constantly watch availability of brake liquid in a tank, without allowing an exposure of its bottom as thus air again will get to system.


Pumping – use of a set of pumping under pressure

Use of a set of pumping under pressure demands giving to it the compressed air for what it is possible to use the beefy tire of a spare wheel. Reduce pressure in the tire to the size specified in the maintenance instruction of a set.


Prevention

Mercedes-Benz recommends to use the compressed air submitted under the pressure of no more 2nd bar.


Connect the filled brake liquid the container to a popolnitelny tank of the main brake cylinder. Process of pumping begins after unscrewing of the union of pumping on a turn half. After when the effluence of brake liquid with vials of air will stop and only pure brake liquid will follow, screw up the pumping union against the stop.

When pumping by this method a large amount of liquid for hydrosystem is necessary to prevent air hit in the main brake cylinder in the course of pumping that often occurs, if liquid level in a tank is not supported.

Pumping by pressure is especially effective, when the system is difficult for pumping or when complete pumping of system is spent during usual replacement of brake liquid.

All methods

After completion of process of pumping strongly press a brake pedal, thus it should pass about a half of the course. Wash away all traces of the spilled brake liquid and tighten unions of pumping the demanded moment, then establish on them dustproof caps.

Check level of brake liquid in a popolnitelny tank of brake system and, if necessary, add brake liquid.

Remote brake liquid should not be used more. Pure brake liquid should be stored in a tight vessel as it is very hygroscopic that lowers temperature of boiling and worsens technical characteristics of brake liquid.