Date:         Tue, 25 Sep 2001 21:30:03 -0700
Reply-To:     Michael Samson <msamson@LOCALNET.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Michael Samson <msamson@LOCALNET.COM>
Subject:      Ken's Whining PS Pump Problem
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When I was a younger man I once worked for an auto parts jobber. As part of that experience I profited on several occasions by being sent to some truly excellent manufacturer's schools, one of which was the Gates Rubber Company's Hydraulic Systems Training Course.

Ken, what you may be dealing with is not the PS pump at all, but instead the pump's reaction to an incorrectly constructed high-pressure line, or otherwise a malfunctioning by-pass valve in the steering rack.

In terms of pure theory, any hydraulic circuit (any type of fluid in a tubular conduit- water, oil, etc.) will, by its very nature, be noisy. As an example, just listen to the water rush about in the pipes in your house, or the effects of air on a pump. Also note the noise characteristics when water moves through differents types (and even sizes) of tubing. One would expect a high noise chatacteristic with copper pipes and very low with garden hose.  Thus, noise is dealt with in such systems via any "shock absorbing" device or design: pressure accumulators, massing, trapped-air locations, by-pass/ relief circuits, and, most notably, tubing materials. In automotive
systems, noise is typically dealt with via accumulators, _by-pass valves_, or _shock absorbing hose assemblies_.

Most types of hydraulic hose are specifically rated for their noise characteristics, and several types are specied as _NOT FOR PS APPLICATIONS_. Many types of steel-braid hoses are incompatible with quiet operation, for the braid can be so rigid as to transfer the energy of fluid pressure/ pulsing into a "harping" sound. This can resonate either from the line directly, and in some cases, even from the pump. I noted that the offending vehicle's lines have been replaced. Were they replaced with OEM grade materials, or made-up/ generic equivalents? Also, are the hoses _securely_ attached to the chassis?

Otherwise, I'd have a look at the rack. To do this correctly, one would need access to a set of hydraulic pressure gauges. I once saw a Saginaw PS box which had a by-pass valve stick in the closed position (that is, maximum resistance to flow). The pump was thus always working "against a load," i.e., at maximum pressure. Talk about Moan and Groan!

Let me know if this helps.

-Michael Samson