Power steering pump question

Bernie Benz b.benz at charter.net
Wed Dec 1 22:28:35 EST 2004

> From: Tom Ellis <tom at tomellisphoto.com>
> Hi Bernie,
> You were right, the problem was one of the X plugs at the top of the unit,
> located (unfortunately) under the bracket where it could not be reached
> without removing the pump.  I pulled the pump and replaced all of the
> o-rings.  There was only one that showed any signs of damage/wear, but with
> luck I now won't have any further problems with the pump.  It turned out
> that the correct o-ring size was a 2-017, the 2-018 was just slightly too
> large.
The pressure forces the O-ring outward against the bore of the pump body
into which the cylinder head screws.  A to small O-ring will be stretched to
do so and therefore is reduced slightly in CS, and thus more likely to leak
if the friction of turning the cyl head is not exactly consistant around the
full circumference of o-ring. Thus, the correct fit is to the pump bore, not
to the cylinder head OD. and the need for a good extreme pressure lube on
the O-ring when installing.

> Neither o-ring was exactly the same CS as the original (which was
> slightly thicker, but not 3/32) but I'm hoping the difference in CS is small
> enough to make no difference.
Any elastomer will change its volume when aged in a specific fluid and
temperature.  Don't compare the dims of an old O-ring to its new
> Please tell me more about the hydraulic fluid you're using in place of
> Pentosin.  Is this also a mineral oil product?
Yes.  I have used tractor hyd fluid only because I had it on hand.  Engine
oil should do just as well.  Just don't use auto trans type PS fluid, while
it has great shear strength, it does not have the lubricity needed for this

Bernie, list contrarian

> Any ideas on places locally
> that might carry it (auto parts store, etc.)?  I used the last of my
> Pentosin to finish this project, and if I can avoid buying more that would
> be wonderful.
> Once again, thanks for the help.  I'd hate to have to keep this beast
> running correctly without help from people like you!

> Tom
> on 11/29/04 7:23 AM, Bernie Benz at b.benz at charter.net wrote:
>>> From: Tom Ellis <tom at tomellisphoto.com>
>>> Date: Sun, 28 Nov 2004 23:18:29 -0800
>>> To: Bernie Benz <b.benz at charter.net>
>>> Subject: Re: Power steering pump question
>>> Hi Bernie,
>>> To determine where the leak is coming from I first power-washed the pump and
>>> surrounding engine area, and then dried everything using compressed air.  So
>>> I'm reasonably certain that the problem is in the area that I described -
>>> the only problem is that there are several possibilities for a leak in that
>>> area.  Those being the two X plugs, the seals on the front banjo (which I
>>> already replaced) and (less likely) a bad/broken banjo fitting (not evident
>>> on inspection, but still an outside possibility).
>> Most likely the cylinder head seals.  I've not had these leak on the 200 yet
>> and they are easier to get at on the 5Ks.  With the pump out and not knowing
>> for sure which are leaking you might want to replace all 7 X head seals.
>>> I'm going to pick up a couple of o-rings tomorrow and try my luck at
>>> replacing the possible culprits.  Unfortunately I don't think that I can get
>>> to them without pulling the pump, due to the mounting bracket.  But such is
>>> life.  And I do so enjoy getting greasy!
>>> I'd love to hear more about your use of hydraulic fluid rather than
>>> Pentosin.  That stuff is so overpriced I can't believe it.  I hadn't
>>> remembered just how bad it was until this leak incident, since I've never
>>> really had to buy it in the past.  When you changed over to the hydraulic
>>> fluid did you drain the whole system first, and if so how did you do that?
>> I just started adding the new fluid.  Never drain the complete system unless
>> you need to R&R the rack.  Do remove the filter screen and clean it when you
>> add new fluid.
>>> Thanks again for your help!
>>> Tom
>>> on 11/28/04 12:02 PM, Bernie Benz at b.benz at charter.net wrote:
>>>> Tom,
>>>> Sounds like there is nothing seriously wrong with your pump, just a
>>>> cylinder
>>>> head seal needs replacing.  A common problem, aggravated by poor
>>>> installation practice.  Clean the pump thoroughly with solvent to remove
>>>> all
>>>> external oil to isolate the exact leak location(s).  Sounds like you are
>>>> pretty sure of the one location, so replace that one first, an easy in situ
>>>> location.  On the under side one checks by feeling for oil, after the
>>>> cleaning.
>>>> The X cylinder heads can be removed with a large screw driver or cold
>>>> chisel, tapping in the CC direction.  The cyl head O-ring is a generic
>>>> 2-018, .875" OD X 1/16" CS, worth about 10 cents.  Available from any seal
>>>> or bearing supply or a good hardware store.  When reinstalling, grease the
>>>> O-ring well with an EP type grease, i.e. graphite or CV grease.  Hyd fluid
>>>> is not good enough to prevent localized stretching of the O-ring.  The X
>>>> heads need only be installed snug with a screw driver, not super tight.
>>>> Pentosin, what's that?  I've been using Ford tractor hydraulic fluid for
>>>> years, not much though, as I don't tolerate leaks.
>>>> Regards,
>>>> Bernie Benz
>>>> Gardnerville, NV
>>>> '90 90Q-20V  160K
>>>> '91 200Q-20V 185K
>>>> Ford "Quatro" Tractor
>>>> Other Misc. Toys
>>>>> From: Tom Ellis <tom at tomellisphoto.com>
>>>>> Date: Sun, 28 Nov 2004 10:41:41 -0800
>>>>> To: Bernie Benz <b.benz at charter.net>
>>>>> Subject: Re: Power steering pump question
>>>>> Hi Bernie,
>>>>> As best I can determine, I have a leak at one of the X plugs on the top of
>>>>> the pump, right next to/under the hose that runs down to the accumulator.
>>>>> Since both the hose and the mounting bracket hide this plug I can't be
>>>>> certain this is the culprit - I first thought the sealing washers on the
>>>>> front banjo fitting were bad, but replacing those hasn't helped.  But
>>>>> since
>>>>> it is impossible to see much of what is happening in that area due to the
>>>>> obstructions I'm not positive that's the problem, though I'm certain the
>>>>> leak originates in this area.  And the leak has been getting progressively
>>>>> worse.  I stopped driving the car last week when I discovered I was
>>>>> running
>>>>> through Pentosin at a truly alarming (and expensive!) rate.  I've been
>>>>> unable to find a used pump locally (Seattle area) for either the 20v
>>>>> engine
>>>>> or the standard 100/200 model and have sent out requests to several
>>>>> wrecking
>>>>> yards on the Internet - hopefully I'll hear something on Monday.  Worst
>>>>> case
>>>>> I can get a new (and "correct") pump from SJM for $375 plus core,
>>>>> shipping,
>>>>> etc.  But if the "correct" pump isn't a necessity I'd rather not pay the
>>>>> premium.
>>>>> Do you have any idea why the pump for the 20v engine is a different part
>>>>> number than the 10v version?  And of course the price is also ~30% higher!
>>>>> Thanks for your help,
>>>>> Tom
>>>>> on 11/27/04 7:15 PM, Bernie Benz at b.benz at charter.net wrote:
>>>>>> The 44 chassis pumps and racks at least from '87 thru the S cars are very
>>>>>> similar and interchangeable, if attention is paid to slight differences
>>>>>> in
>>>>>> banjo fittings and bolts, etc.
>>>>>> What are the symptoms of your dying pump?
>>>>>> Bernie
>>>>>>> From: Tom Ellis <tom at tomellisphoto.com>
>>>>>>> Date: Sat, 27 Nov 2004 18:53:24 -0800
>>>>>>> To: <b.benz at charter.net>
>>>>>>> Subject: Power steering pump question
>>>>>>> Hi Bernie,
>>>>>>> The pump on my 200 20v is dying and as I've been searching for a
>>>>>>> replacement
>>>>>>> I was a bit surprised to find that (so far as I have been able to
>>>>>>> discover)
>>>>>>> this pump is unique to this model car.  Do you know if the "official"
>>>>>>> pump
>>>>>>> for this car is the only one that will work and if so, why this is?
>>>>>>> Looking at the pump, it appears to be virtually identical to the pumps
>>>>>>> used
>>>>>>> in the '89-'91 100/200 series Audis - except for the part number.  While
>>>>>>> I
>>>>>>> haven't tried to do so, it sure looks like these other pumps should bolt
>>>>>>> on
>>>>>>> just fine.  But not knowing just what those crazy Germans were thinking
>>>>>>> about when they designed the pump for the 20v, I'm a bit wary to just
>>>>>>> throw
>>>>>>> one on to see what happens.
>>>>>>> You clearly know a lot about these cars, and I'm hoping that you might
>>>>>>> have
>>>>>>> some experience with the pump interchange question.  Any insights you
>>>>>>> can
>>>>>>> give me will be greatly appreciated!
>>>>>>> Thanks,
>>>>>>> Tom Ellis

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