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Home >> Mercedes Benz >> 2006 >> G55 >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Brakes -- Basic Knowledge -- G-Class (463) >> Basic Knowledge >> Brake master cylinder, location/task/design/function - GF42.10-P-3100GG

Brake master cylinder, location/task/design/function - GF42.10-P-3100GG

MODEL 460, 461.217 /219 /223 /227 /229 /238 /239 /249 /266 /267 /302 /321 /322 /323 /326 /327 /328 /329 /331 /332 /335 /336 /337 /338 /341 /342 /345 /365 /366 /367 /368 /401 /402 /403 /404 /405 /450 /451 /452 /454 /455 /456 /458 /459, 463 

Task 

Producing the braking force for the wheel brakes with the help of brake fluid

Design of brake master cylinder models 460, 461 (vehicles without ABS) 

Fig 1: Identifying Design Of Brake Master Cylinder
G07741522Courtesy of MERCEDES-BENZ USA

Design of brake master cylinder model 463 with ABS 

Fig 2: Identifying Design Of Brake Master Cylinder
G07741523Courtesy of MERCEDES-BENZ USA

IMPORTANT The brake master cylinder has an intermediate piston with integrated central valve, which means that the compensation bore in the intermediate piston brake circuit is no longer used. This function is assumed by the central valve.

The central valve prevents the primary cup seal of the thrust rod piston being damaged at the compensation bore due to pressure fluctuations which are produced by the ABS control processes during brake pressure build-up

REFER TO BASIC KNOWLEDGE Function Model 463 with ABS
The intermediate piston (8) provided with a longitudinal slot is guided in the cylinder bore by a roll pin (7). The roll pin serves as a stop for the intermediate piston, to open the central valve and at the same time as a replenishing bore.
When the thrust rod piston (17) is operated, first the primary cup seal (6b) moves over the compensation bore. Then the intermediate piston (8) is moved forwards due to the pressure build-up, causing the central valve, consisting of components (3, 4 and 5), to close.
Both pressure chambers are now closed and the required brake pressure can be built up.
When the brake pedal is released, the two pistons (8) and (17) are pushed back due to the tension force of the compression springs (2) and (10), the valve pin (5) contacts the roll pin (7) acting as a stop and opens the central valve.
Pressure and volume can be compensated.