Replacing the power brake seal – TEDGUM 00748698 (Manual #33)

Loss of tightness on the working piston is a common brake servo failure. The symptom of the fault is a characteristic hissing sound when pressing the brake. This fault can be easily repaired by replacing the gasket with a new one. The replacement process is not complicated, but care must be taken not to damage the piston surface. Even a minor scratch on the piston may result in the need to replace the entire element.

We present below the subsequent stages of replacing the gasket:


Remove the used seal, preferably with a plastic spatula, so as not to scratch the internal piston. Even the smallest scratch may lead to loss of tightness, which will result in the need to replace the entire element.


After removing the old seal, thoroughly clean the outside of the piston. Then thoroughly lubricate the new gasket with the included silicone grease on the inside and the lower part to the flange on the outside. Only silicone grease should be used, as other substances may weaken or damage the element over time.


Push the lubricated sleeve onto the piston so that it is right next to the housing.


The auxiliary sleeve should be put on from the top, press it against the seal and at the same time use a spatula to evenly press the seal so that the edge fits into the metal housing of the servo.


If the lower edge is fully inserted into the housing, strike the support sleeve evenly and gently with a hammer to press the seal down to the flange line. The gasket flange should adhere to the housing along its entire length.

Once the seal is installed, the servo can be reinstalled in the car.

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