General information about the brake system and safety precautions (Mercedes-Benz G-Class W463)

General information

The front and rear of all models considered in this Manual are equipped with disc brakes with fixed-type calipers at the front and floating-type calipers at the rear.

The brake system consists of a master cylinder, a vacuum booster and disc brakes on the front and rear wheels and is divided diagonally into two independent hydraulic circuits. If any of the circuits fails, (for example, as a result of a breach in the seal) the second continues to function in normal mode, providing adequate braking of the vehicle. Additionally, a pressure regulator valve is built into the circuits of both rear brake mechanisms, providing dynamic adjustment of the braking force of the rear wheels in accordance with the change in load on the rear axle of the car. The fluid pressure in both circuits is created by a tandem-design master brake cylinder (MBC). The MBC is activated when the foot brake pedal is depressed.



A brief description of the operating principles of the auxiliary electronic systems anti-lock brakes (ABS), emergency brake assist (BAS), traction control (4-ETS) and anti-skid (ESP) is given in Part Operating techniques and auxiliary systems.

The brake fluid reservoir is attached to the master brake cylinder (MBC) and supplies the entire hydraulic tract of the brake system with working fluid.

On petrol models, the brake booster accumulates part of the vacuum created in the engine intake manifold. On diesel models, due to the absence of such a source of vacuum, a special vacuum pump is used. If necessary, a special valve ensures the connection of an appropriate source of vacuum, thereby increasing the effect developed by the foot brake pedal.

The hand-operated parking brake acts via cables on special shoe assemblies that are part of the rear wheel disc brake mechanisms.

Procedure to follow when the ABS warning light comes on while driving

1. Stop the car, turn off the engine and start it again.

2. Check the battery voltage level - if the measurement result is less than 10.5 V, recharge the battery.

Note: If the ABS warning light comes on when you start driving and then goes out after a while, this indicates low battery voltage, which increases after the generator starts working.

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3. Make sure that the wire tips are securely fastened to the battery terminals; tighten the fasteners if necessary.

4. Jack up the car and place it on supports, remove the wheels and check the condition of the wheel sensor wiring.



5. More detailed diagnostics should be performed at a service station using special equipment for reading fault codes (DTC) recorded in the control module memory.

Security measures

• Brake fluid is a highly toxic and chemically aggressive compound and when in contact with body panels it destroys the paintwork!
• Brake dust generated during the wear of brake pads may contain asbestos, which is harmful to human health - do not inhale it under any circumstances when cleaning brake mechanisms!
• Working with the brake system requires special cleanliness and strict adherence to instructions. If you do not have the necessary experience, it is advisable to contact a service station.

Note: When driving on wet roads, it is necessary to periodically press the brake pedal to remove moisture from the brake discs.

• During the rotation of the wheel, moisture is thrown off the brake discs under the action of centrifugal force, but a film of silicone, rubber abrasion products, grease and other contaminants remain, reducing braking efficiency!
• After installing new brake pads, the latter must be worked in - try to avoid sudden braking for the first 200 km after replacement!
• Corroded disc brakes create a shaking effect when braking that does not disappear over time - replace the discs!
• The burning of dirt onto the surface of the brake pads leads to the formation of grooves on the surface of the brake discs, which leads to a decrease in braking efficiency!