an exhaust brake incorporates a slide valve with a decreasing returning or opening effort without also having an increased working or closing effort of its valve elements incorporated therein . the brake system includes a first valve piston connected to a closing slide valve and adapted to move in reciprocating motion inside a cylinder under an operating pressure supplied thereto , and in addition , a second valve piston adapted to be driven in rectilinear motion under the operating pressure in the cylinder so as to work upon a resilient member to be deformed resiliently . when opening the slide valve , a restoring effort of the resilient member is relayed effectively to the first valve piston through a transmitting member to work in assistance with the returning motion of the valve piston .