From Googling around it seems that high flow rates cause cavitation in the
pump which makes the noise.
I guess the pump likes to see some head pressure to run quietly.
BTW, this isn't a Vanagon specific problem; I got this info from a Maxima
board.
A link to a hose repair shop says this is a common problem on European and
Asian makes.
But, a Chrysler minivan forum also brings up the issue, so I would say it's
almost universal.

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
JRodgers
Sent: Tuesday, July 10, 2012 8:08 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: power steering

Larry, I haven't a clue, myself, as to why that restrictor is needed.
But in my own experience, the restrictor  must be there. I had to
replace that short pressure hose with the restrictor. I did it with a
hose that had no restrictor. I went through 5 pumps thinking they were
all bad, given the racket they were making, and three of those pumps
were brand new remanufactrure pumps. I sent them all back as bad pumps.
I was totally embarassed when I learned of the fix. Dennis Haynes or
Scott Daniels - can't remember which - told me about  having to have the
restrictor else I would have lots of noise like a bad pump. Turned out
to be true. Lots of noise. Replaced the non-restrictor hose with one
with a restrictor, noise was gone. Just my experience.

John

On 7/10/2012 6:48 PM, Larry Alofs wrote:
> What is the purpose of the restrictor anyway???
>
> Larry A.

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