Hello. The noise in the hydraulic system of the direction can have various causes within which, the most common are cavitation (by air entrance to the pump suction either by some lazy clamp or damaged hose), low oil level or in the worst case occurrence of damage to the internal parts of the pump.
For the first two cases, the problem is solved correcting the condition and for the third case the pump must be repaired or changed while making flushing to the system in order to evacuate all the materials that have traveled through the hydraulic torrent and may affect other components.