<p>A system for mounting or/demounting a cylinder unit (1) in a vehicle. A piston rod (5) provided with a piston (4) arranged in the bore (6) of the cylinder unit (1) which piston (4) and piston rod (5) are displaceably arranged in the axial direction of the bore (6) of the cylinder unit. The bore (6) has an opening (13) provided for an end portion of the piston rod (5) to protrude out from the bore, and the piston (4) separates the cylinder unit into a first chamber (7) and a second chamber (8) . At least a first passage (9) is provided for communication of fluid into or out of the first chamber (7) . In an initial operating position of the cylinder unit, the piston (4) and the piston rod (5) is positioned with the end portion of the piston (5) protruding out from the mouth of the bore (6) . In a mounting/demounting position of the cylinder unit, pressuriized fluid is introduced into the first chamber (7) preferably through the first passage (9) thereby placing the piston (4) and the piston rod (5) in a mounting/demounting position where the end portion of the piston rod (5) essentially retracted in the bore. The invention also concerns a method for mounting/demounting the cylinder unit.</p>
