Working on a question today involving a slow leaking Mercedes steering rack. The leak was coming from one of the hard lines. The questions are; What are the hard lines and how do you fix it?

See the attached image of the steering rack. The hard lines come from the pinion housing to the body of the rack. To make power steering work, these lines move fluid to different parts of the rack to help with the assist. In a power steering system, the fluid both ‘pushes’ the rack to that direction and ‘pulls’ the rack back in. In order to move the rack back to center, you need to press from the outside, and thus the hard lines. The hard lines will bring fluid to the outside of the rack and enable that ‘pulling’ action.

Hard lines are different that steering hoses. Steering hoses come from the pump and are usually rubber with metal fittings. That hard lines are all metal and thus the ‘hard’ lines name.

The question now is how to fix the leak. You can try removing the hard line, replacing the O-ring that is under there and tightening down. Sometimes this will stop the leak, but if something is warped or damaged there, you will have to replace the whole steering rack. You cannot purchase the hard lines separately. They are considered part of the rack. Hoses can be purchased separately