[s-cars] Power steering pump resistance?

[Aaron Ryba]

Randy, you are correct on the typo. Just trying to keep things intersting here!
When I had the hoses disconnected, IIRC specifically the J hose that leads to the brake pressure accumulator/bomb the pump turned without any resistance. After some thought I think the problem may be the pressure release valve or the check valve in the bomb that is malfunctioning.  The reservior seems to have adequate fluid which does not change often after sitting overnight (leaky relief valve) or overflow. There is adequate brake pressure and the brake pressure light has only come on once or so after the car had been sitting for a week or two without driving. Here me out....

When I replaced the original high pressure hoses with new Spokane HOH ones there was some debris in the integrated filters in the banjo bolts and in the reservior filter too which I cleaned out upon flushing the system.
My thought is that there is some debris stuck in either the relief valve or the check valve of the accumulator/bomb that is making operation difficult. Most likely it is the relief valve (where the hydro fluid would be passing though most of the time when brake pressure is adequate) that is the culprit (?). Correct me if I am wrong. Perhaps the debris is not causing the valve to fully malfuntion either in closed or open position but just more difficult to operate thus the increased back pressure on the power steering pump and then on the belt tensioner pulley.
IIRC the hoses went bad after I replaced the bomb with a newer unit, so the debris could have lodged in at that point.
I did notice that upon installing the new HOH lines there is some whine noise from the pump, mostly noticeable from the interior. I called HOH and made sure that they did keep the restrictor in the new hose build. I assumed this noise was just how the new hose functioned or perhaps some damage that had been done to the pump when the old hoses broke and some debris passed though. I now think it could be caused by the additional load put on the pump by this malfunctioning release valve.
The tensioner is only about a year old and upon removing it and inspection the bearing and the spring both seem to be in proper working condition. The belt which is new also looks good and shows no sign of stretching (measurement confirmed). I think the tensioner is exhibiting this clicking noise due to the added load on the system via the pump/check valve issue. The belt & tensioner operate smoothly at higher rpm but at idle with some load on the engine (turning steering or AC on) I do notice the tensioner rattle when the clicking noise is made. It is exhibiting the same behavior the old one did before I replaced it along with the pump, hoses, filters, banjo bolts fluid & swapped out the bomb.
If I had access to another 20vt car I could swap out the tensioner and bomb easily to see if those parts work properly but I don't think that is an option here down in Spartanburg SC!
I did replace the original bomb with a newer one about 9 months ago and my low brake pressure problem went away. I though about swaping the old one back in to see what happens to the pump backpressure situation but since the unit was malfunctioning already it may be hard to determine any reliable difference.
The best solution I think is to have a pressure testor hooked up to the brake servo as Bentley suggests. I guess that means taking it to the a shop and spending some $$ which is probably cheaper than buying the tool myself (VAG 1441 $318) or purchasing a new bomb (if that is even the problem).
One last thought is that perhaps the newly fabricated J-hose by Spokane HOH with the integrated origianl restrictor could be the culprit. However my understanding is that Spokane is somewhat of an authority on rebuilding these things and it would be strange that I am the only user who has experienced this problem.
Hopefully the lenght of my response here doesn't imply that I have found a solution. Please reply with any other comments you may have. This is bugging the heck out of me!
Aaron


----- Original Message ----
From: Tom Green <trgreen at comcast.net>
To: s-car-list at audifans.com
Cc: Aaron Ryba <aaronryba at yahoo.com>
Sent: Thursday, May 29, 2008 11:28:39 AM
Subject: Re:[s-cars] Power steering pump resistance?

I don't recognize your difficulty in rotating the pump as anything I  
have encountered
with the pump, Aaron.  My experience is it is difficult to keep the  
pulley from turning.
Perhaps if you remove one of the hose connections or loosen it to see  
if it could be
caused by blockage in the line.  I am thinking that some debris may  
have caught in
the orifice or screens in the banjo fittings.

Do you see significant movement in the tensioner and serpentine belt  
or does it
operate smoothly?  Has the spring in the tensioner failed as well as  
the bearing?
I assume the belt is wearing excessively as well?  Have you rebuilt  
the tensioner with
new bearings?

It is a piston pump, Randy, but a somewhat sophisticated design with  
a high flow but
variable output for the steering and less flow but high pressure for  
the brake booster.

Tom

> D0ate: Wed, 28 May 2008 12:22:58 -0700
> From: "McCall, Randy" <rmccall at nexant.com>
> Subject: Re: [s-cars] Power steering pump resistance?
> To: <s-car-list at audifans.com>
> Message-ID:
>     <99A2815FF4D295488E034407278B16A401E294C7 at sacexm01.nexant.corp>
> Content-Type: text/plain;    charset="us-ascii"
>
> Aaron,
>
> I wasn't aware that serpentine belts used retired people on  
> pensions for
> bearings - I can certainly see why they would wear out as old as they
> must be; but I'll assume that's just an amusing typo ;-)
>
> After just finishing up a t-belt R&R this past weekend due to a failed
> water pump, I can tell you that the PS pump on my 95.5 S6 turns with
> relatively light resistance - I believe its a piston pump, so perhaps
> one of the valves controlling pentosin flow is not functioning  
> correctly
> in your pump (although pentosin is not a compressible fluid, so I'm  
> not
> completely sure about how pressure is acheived - spring loaded
> checkvalves?). In any case even with the pulley removed, the pump  
> flange
> was relatively easy to move through a rotation, and I can't recall any
> portion of the rotation cycle that was high resistance (clear
> compression areas in the pulley rotation cycel are there, but not at
> high resistance).
>
> -Randy
> 95.5 S6A
>
> Date: Wed, 28 May 2008 08:20:46 -0700 (PDT)
> From: Aaron Ryba <aaronryba at yahoo.com>
> Subject: [s-cars] Power steering pump resistance?
> To: s-car-list <s-car-list at audifans.com>
> Message-ID: <207244.24888.qm at web51410.mail.re2.yahoo.com>
> Content-Type: text/plain; charset=us-ascii
>
> O-holy S-list,
>
> I am trying to troubleshoot why I am prematurely wearing down serp  
> belt
> pensioners/bearings.
>
> Can anyone tell me what kind of resistance if any should be  
> expected on
> rotating a power steering pump by hand (all hooked up with fluid, belt
> off, etc.)?
>
> I am getting some significant resistance for about 60 degrees of
> rotation.
>
> TIA
> Aaron Ryba
> 95 S6