Ping Jim Warman - Power steering still not working correctly

I posted a few weeks ago about my power steering not working correctly even after I replaced the pump and the rack. I took the truck off-roading a few
weeks back and when I pulled back onto the road the power steering worked perfectly. It stayed this way for 4 days but since then it has been the same; not working so well anymore. I can turn the wheel, but it "hangs up" in a few spots either side of center.
Jim, I followed your method of bleeding the steering system. I jacked up the front end and, with the engine off, turned the steering wheel from lock to lock a few times. Things still seemed to get "hung up" in those same spots. This tells me that the problem is obviously in the rack and not in the pump.
It baffles me how the steering would work only partly, then work perfectly for 4 days, then work partly again but get hung up in certain spots. By hung up, I mean that the steering wheel feels like its sticking in those spots and when making a turn, when the wheel gets to one of those sticky spots, it stops returning to center and holds where it is. I would turn in circles if I didn't straighten the wheel myself.
How likely is it that I replaced my defective rack with another defective rack? Could there be debris lodged in the rack? Is there any way to install a filtering device on the low pressure line?
Thanks for the help guys, this one has baffled myself and all of my mechanic buddies.
Here is a link to the previous discussion. http://makeashorterlink.com/?N25441388
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Dave Earle
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Let me throw this out there for discussion: Would this be a binding lower ball joint? The fact that you went off roading and then it worked ok for a few days suguests that something in the steering got "twisted/moved/repositioned in the off roading and then poped/worked its way back into place to cause the stick/binding problem again. I may be out in left field, but since you have replaced the pump and the rack, I'am thinking ball joint or outer tie rod end. Also one other idea: Jim could answer this better than I: Did the replacement pump include the pressure relief valve? wth

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Seems to me I recall you saying that an alignment shop had check the front suspension for binding parts but I can't recall the exact circumstance. As wth has mentioned, there remains the possibility that a binding ball joint is binding intermittently but it would be tough imagining it would be a stick/slip/stick/slip scenario. The rack is also a possibility but I'd expect something like "morning sickness" or some other steady state concern.
There's also the remote possibility that something is amiss in the column.... especially if the concern happens when the wheel is in roughly the same juxtaposition when the concern raises it's ugly head.
You might approach the alignment shop with this new info and they might be able to diagnose it a little less painfully...
HTH.

even
few
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wth, the outer tie rod ends are fine, I inspected them when I removed them to replace the rack. The ball joints seem fine and were OK'd last time it was inspected, but even if they needed replacing, I don't think the steering would stick in exactly the same spots with no weight on the front end. Jim mentioned the pressure relief valve and said its inside the pump. I would have to assume its in there, especially since there was a period where everything was working beautifully.
Jim, I never brought the truck into an alignment shop. I and a few mechanic friends looked at the truck and everybody agreed that it was most likely the rack, some suggested also replacing the pump so I did both. The truck is driveable at the moment (much easier than when the power steering didn't work at all) so I'll live with it for now and see what else I can find. The warranty on the rack is only 3 months so I'll bring it to some garages and get some more opinions in the near future and figure out if I'll be replacing that rack again.
Thanks for your responses and ideas,
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Dave Earle
97 Explorer Limited
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