Abstract: A device is provided for bleeding entrapped gas from a master brake cylinder assembly when the latter is removed from a vehicle or prior to the assembly being installed in the vehicle and all of the outlet ports of the assembly are plugged. The device includes a support member having an upright section with a transversely extending passage formed therein. Removably mounted on one side of the upright section is the master cylinder assembly. The assembly is positioned so that an access opening which is formed in one end of the cylinder assembly to provide access to an end portion of a primary piston of the assembly, is aligned with and is adjacent to the passage in the upright section. Disposed in spaced relation to the opposite, or second, side of the upright section is an actuating unit which is mounted on the support member for selective manual adjustment between operative and inoperative modes.