Abstract: A hydraulically damped mounting device has first and second anchor parts connected by a first deformable wall, and a working chamber for hydraulic fluid partially bounded by the first deformable wall. The working chamber is connected to a composition chamber for the hydraulic fluid by a first passageway, the composition chamber being partially bounded by a second deformable wall. There is also an auxiliary chamber partially bounded by a third deformable wall connected to the working chamber by a second passageway. The mounting device then has a vacuum chamber connectable to a vacuum source for varying the pressure in the vacuum chamber.