I have a 1963 model MF 202 in my shop with steering problems. I first replaced the pump due to low pressure issues. Power steering still not working. I removed the control valve mounted on the steering column. There does not seem to be any internal O-rings or seals, only the ones to keep oil...
Hope this turns out to be a good source of information. I repair tractors for extra cash. I seem to attract older stuff that is hard to find parts and information for.