Abstract: An apparatus for detecting leaks in a test object having chamber walls, having a first and a second side subject to differential pressure produced by production of a partial vacuum on the first side, the detection being carried out by use of a test gas present on the second side of said chamber walls. The apparatus has a vacuum pump for providing the partial vacuum, a detector for detecting the test gas, a connecting means for connecting the apparatus to the test object, and a plurality of primary control valves for controlling the leak detection process. The improvement comprises at least one of the primary control valves being actuated by a driving cylinder and a driving piston, where the piston is actuated via pneumatic actuation which is provided by the vacuum pump while the test object is connected to the apparatus.