Intermittent P/S

Mike Miller mikemilr at
Fri Jan 10 08:44:27 EST 2003


My problems was fixed by replacing the pump. I did not have the time to do
it myself so I do not know if the bottom of the pump was dry or not. I
suspect it was. I watched a couple times as the fluid foamed out the top of
the reservoir. That made a nice mess. My level would drop down to about 3/4
inch below the min mark, which would trigger the low fluid alarm.

The main thing I noticed before I ever got any low fluid alarms was that the
initial resistance to turn the wheel was greater. It's hard to describe.
Things like pulling into a parking space - I would overshoot a bit because
the car was "slower" to respond to what was "normal" steering input. I would
start the turn and then realize I needed more force on the steering wheel to
get it to begin to turn. Driving on our twisty roads felt a little different

I did play with it a little by filling the reservoir to the max, then, with
the car idling and the hood up, ran the steering wheel almost lock to lock a
few times. That was enough to get the fluid volcano out the top of the

hope that helps,
mike miller
helmville mt

----- Original Message -----
From: Scalmanini Steve
To: 200q20v at
Cc: Mike Miller ; b.benz at
Sent: Friday, January 10, 2003 2:44 AM
Subject: Re: Intermittent P/S

Mike, I didn't ask and you didn't volunteer if
simply changing the pump solved your problem of
pumping foaming Pentosin out of the reservoir.

My symptom continues like that.  P/S is intermittant;
fluid level remains about 1/3 full and returns to
that level shortly after adding any.  If I refill,
the fluid above that level is gone within a few
minutes of driving.  Brake boost is normal.

Blau refuses to honor ZF's 3-year warranty on the
pump.  ZF says their 3-year warranty supercedes
Blau's 1-year so their going to have a little chat
about that with their distributor for Blau.
(' can't wait to hear how that goes.)

Regardless of that, ZF is willing to replace the
pump themselves if Blau won't, --IF-- that's the
problem.  But since air is possibly being pumped
into the reservoir, they assume it's getting in
somewhere, so there must be a leak in the system.
I think if there was a leak, the fluid level would
continue to drop after reaching it's current level
of ~1/3 full, but it's not.

So, when you had this same symptem, did you solve
it by only changing the pump?  If so, was the
pump dry underneath, such that no fluid had been
leaking from it, and assumedly no air had been
leaking into it, and therefore (Sherlock speaking
here) the problem had to be only with the pump?

Maybe, on the other hand, the pump is somehow making
the fluid foam on its own (i.e. without any air
from outside the system).  I have no idea if this
is possible, and being hydraulic fluid, I thought
it couldn't.

Anyway, let me know how you fixed yours,



PS to Bernie: the guy at ZF mentioned in passing
in our conversation today that when the rack was
at either maximum end of travel, an overpressure
relief valve would kick in to limit the pressure
on the seals that so commonly fail.  That was the
first I'd heard of this valve so I thought I'd pass
it along.

--- Mike Miller <mikemilr at> wrote:
> This sounds a lot like what mine did when the PS
> pump started going. It took
> extra effort to get the wheel to start turning, then
> it felt fine. After
> about a week of this, I had foaming pentosin coming
> out the top of the cap.
> mike miller
> helmville mt
> ----- Original Message -----
> From: "Scalmanini Steve" <sscalmanini at>
> To: <200q20v at>
> Sent: Saturday, December 28, 2002 4:17 AM
> Subject: Intermittent P/S
> > Does anyone know what the likely problem is for
> power
> > steering that has been intermittent starting five
> days
> > ago.  Sometimes it seems fine, but most of the
> time
> > it's very hard to turn.

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