steering problems cat chellinger 65

I have a cat chellinger 65 , will not steer , no pressure at steering wheel control . Main steering pump ,boost pump and cooling pump have been sent to a hydraulic repair/ test centre ,, no faults found .This all started after a main hose to the steering motor on rear of transmission blew. Does any one have a schematic on the steering system ,or any clues as to what might be going on here . Would appreciate any response re. the above problem. Adrian