Tractor Repair: Ford 4000 p/steering problem, vent cap, valve unit

Question
Hi,

 Probably a common question, as there were/are many 62-65 Ford 4000 4/cyl. diesels plodding around out there.  Mine is a p/s problem.  P/S line (metal) cracked w/o my knowing it, had to replace p/s pump w/rebuilt unit.  Repairs went ok, but now steering is stiff/tougher (esp. @ lower rpm's), and losing p/s oil from vent cap @ steering unit under steering wheel after an hour or so usage.  Using correct p/s oil.  I think the pump itself is working ok, but almost seems like a 'blockage' somewhere, causing the heavy steering and fluid being forced out @ that vent cap, which is near the control valve unit.  Question...could the lack of fluid for a time, have damaged the control valve, could I have a 'blockage' in the p/s line from control valve to steering cylinder, steering cyl. damage, or something I'm not thinking of.  My p/s pump has a combination flow control/relief valve inside, which they say could be 'shimmed' to give more pressure, but it seems like I have enough pressure, but a different problem.  I am using FO-20 I & T manual.   

Thanks for any/all help or guidance in advance,
Sorry my question was so long, tried to be thorough.....

mal.

Answer
The more info you provide the better I can try to answer your question.
No oil supply will not hurt a valve.
How many hours does this tractor have?
Stiffness can sometimes be caused by air in the system.
Make sure that your cylinder isn't binding up somehow, causing excess pressure. Or a kinked line.
I have replaced steering control valves only to have the pump go bad a week later and vice versa.
Let me know what you find out and we can go from there.
If you would please rate my answer, Thanks