Main brake cylinder, suitable for W124 sedan, coupe and station wagon from model year 5/1987 - 6/1994, for vehicles with and without ABS. Not suitable for V8 models and vehicles with ASR.
This main brake cylinder has three connections: front left, front right and rear.
The main brake cylinder (HBZ) on the 124 is very robust and durable. The wear of the sealing boots is constant, but inconspicuous. Thus it comes with the years to ever worse brake performances by internal leakages.
If the repair with a seal kit is not possible due to internal rusting, the complete replacement of the HBZ is a good idea.
Tip: on the brake fluid reservoir are two rubber caps (w124-hbz-gkb-ate or w124-hbz-gkb-gir), which become brittle and tear due to age. To enable the brake fluid to be changed with pressure equipment, these rubber caps must seal tightly. They should therefore be replaced when working on the HBZ.
