I have a kind of baffling mystery and I hope someone out in list land can help me with it.  I have a customer's van here that has had a whining power steering pump for all the years that I have been working on it (almost 4 now).  The folks initially had a leaky hose which we replaced with a new one, and then replaced the pump with a good used one from a junk yard.  At the time, that pump whined too, and we just wrote it off as bum luck of getting a used pump that was also a whiner.  Recently they brought the van in and asked me to make the whine go away.  I put on a couple used pumps I had here, and both of them whined as well.  Finally they said, "OK put on a rebuilt pump."  I did, but lo and behold it is whining as well and I just can't figure out why.  The system has new fluid in it, the power steering filter has been changed (most of you didn't even know there was such a beast did you?), and everything is tight and not leaking.  The rebuilt pump is from ZF and I would think it a very big coincidence that this was a dud rebuild seeing that any other pump that I put on there also whined.  The only other out of the ordinary thing in the system is the high pressure line to the pump from the steel line that runs under the van.  We replaced it with a line that was made up from a local hydraulic shop and the diameter of the line is a little smaller that the stock line.  We have checked the reservior and supply lines to the pump for obstructions or restrictions, but with no problems found.  Any ideas as to what could be causing this problem?  This is the first time I have had a whining pump problem not be solved by just replacing the pump.

Thanks in advance for any help you can give,
Ken Wilford
John 3:16
www.vanagain.com
Phone: (856)-765-1583
Fax: (856)-327-2242