Hi, it only takes one speck in the wrong place, hydraulic components are made to very close tolerences. I doubt if you can flush it out since you have allready used 7 liters of oil trying. The fluid control valve is in the rack not the pump. I stripped power racks before, but not vovlo ones, and its quite easy as long as you can get all the internal parts (seals). The hard part is getting it out of the car. I would ask around your local shops just in case anyone has seen this problem before, the only trouble is you can allmost predict what they would say.