[s-cars] Upper strut mount R&R time?

[tblack]

Charlie , You may have  the answer! I've heard that air in the system may
cause the symptems that Joe is experiencing. Jack up the front wheels and
turn the steering wheel lock to lock several times and let the list know the
result.
Tom Black
----- Original Message -----
From: "Charlie Smith" <charlie at elektro.cmhnet.org>
To: "Joseph Pizzimenti" <pizzoman at yahoo.com>
Cc: "Audi S Car List" <s-car-list at audifans.com>; "Charlie Smith"
<charlie at elektro.cmhnet.org>
Sent: Monday, December 02, 2002 11:15 AM
Subject: Re: [s-cars] Upper strut mount R&R time?


> Earlier, Joseph Pizzimenti wrote:
> >
> > Okay, guys, I need you on this one as I'm stumped and
> > about to bash my head into a wall.
> >
> > Steering:
> > No Servo relay
> > New rack
> > New bomb
> > New pump
> > New J hose
> > New control arms
> > One new tie rod, other one has fresh ends
> > H&R/Bilstein Sports
> > ASW Camber plates
> > Cleaned out filter in reservoir
> > Flushed and replaced w/new Pentosin
> > ATE Superblue in brake reservoir
> > Big Reds w/Pagid Orange pads up front
> > Both levels fine, but superblue is a little high
> >
> > Symptom:
> > When turning the wheel, intermittently there is what
> > feels like a hydraulic hiccup, i.e., steering will
> > turn normally, but I will suddenly lose assistance for
> > a brief sec and hear a mooing come from the system.
> > Mooing also happened when I was cleaning off the
> > rotors the other night (accelerate to 100 or so at 3AM
> > on straight road and warm up pads, gets rid of noise
> > somewhat from Orange Pads) and as I was coming under
> > 50mph, I heard the mooing again.  Did not sound good.
> > I also get it when the car is starting off and feel it
> > through the steering wheel, as I do when the "hiccup"
> > happens.  Please help, I don't want to break anything
> > else.  Upper strut mounts, perhaps?  I'm at a loss
> > here.
> >
> > Thanks,
> > Joe
> >
>
> Let's consider the situation for a moment.
>
> Since he is losing power assistance to the steering when this happens,
> I think the problem is related to temporary loss of hydraulic pressure.
>
> The bomb stores pressure to preserve the power brakes when the engine
> powered hydraulic pump loses pressure (like when the engine quits),
> it does not provide a backup pressure source for the steering. [* see
note]
>
> This means that even a momentary loss of pressure from the pump will be
> something you will feel in the steering.  Like you said - suddenly lose
> assistance for a brief sec.
>
> I don't know about the "mooing" sound, what's the list think - if the pump
> briefly sucked air instead of pentosin would it make a noise?  What could
> be blocking fluid pickup on an intermittent basis?
>
> If it's something like this going on, I'd think the worst that could
happen
> would be if the pressure loss were prolonged then he might lose power
> assistance for the steering for the duration.
>
> Joe - one way to bleed all of the air out of the pentosin hydraulic system
> is to cycle the steering wheel lock to lock several times.  If your
repairs
> that included replacing the pump and rack are very recent, maybe there's
> still some residual air in the system.
>
> What do other folks think?
>
>     - Charlie
>
>
>
>
>
> [* note]
> The bomb does not store very much fluid under high pressure.  The brake
> assist unit uses very little hydraulic fluid for a single application,
> thus the bomb can provide high pressure fluid for a number of brake
> applications.  On the other hand, the steering rack uses quite a bit
> of fluid volume when you turn the steering wheel; this is way more than
> can be stored in the bomb.
>
> It would be interesting to see the operating pressures of the brake assist
> and the steering rack.  I'll bet the rack operates at a lot lower pressure
> than the brake assist.  Has anyone taken a pump apart to see if it's
really
> set up with a high pressure output (for the brakes) and a lower pressure
> output for the steering?
>
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