Abstract: A pneumatic brake booster for a motor vehicle wherein movements of a control rod (38) determine the openings and closings of at least one axial intake valve (52) and at least one equalizing valve (50). The intake valve (52) being inserted between a pressure source subjected to the pressure (Pa) higher than the first pressure (P1) and a rear chamber (18) of the booster, and the equalizing valve (50) being inserted between a front chamber (16) and the rear chamber (18) to actuate a moving partition (14) located between the front chamber (16) and the rear chamber (18). A tubular element (76) of that is axially offset transverse faces (78, 80) comprised of first elements (82, 84) for sealing the axial intake and equalizing valves (50, 52).