Hydraulic pump rebuild procedure (repost)

[Arun Rao <rao@pixar.com>]

Kneale Brownson asked for this procedure that I posted two years ago: I
figured it might be useful to someone else as well.

Note that it's for the 3B engine, but it's actually quite a bit simpler
on the 10-valvers.

By the way, I followed Mike Arman's suggestion and had a local
industrial hydraulic place rebuild my pump-to-reservoir and brake
MC-to-reservoir return hoses. He did it while I watched (and did a
really clean job) -- all for the princely sum of $20. So if you have
weepy hoses, this is a *good* thing to do.

-Arun
--------------------
Arun Rao wrote:
> 
> > From coimbra.ans.net!owner-quattro Wed Feb 19 19:24:04 1997
> > From: "Arun Rao" <rao@quattro>
> > Message-Id: <9702191706.ZM27708@quattro>
> > Date: Wed, 19 Feb 1997 17:06:47 -0800
> > Reply-To: rao@pixar.com
> > X-Mailer: Z-Mail (3.2.3 08feb96 MediaMail)
> > To: quattro@coimbra.ans.net
> > Subject: Hyd. pump rebuild experience (long).
> > Mime-Version: 1.0
> > Content-Type: text/plain; charset=us-ascii
> > Sender: owner-quattro@coimbra.ans.net
> > Precedence: bulk
> >
> >
> >       Folks,
> >
> >       I resealed the leaky hydraulic pump on my '91 200Q (*way* too
> >       early, at 54K, I think) last weekend, and here's an outline of
> >       the procedure. Hopefully it will be of use to some fellow lister.
> >
> >       Thanks to all the listers who helped in various ways: please
> >       add to or correct the following if I've missed anything.
> >
> >       Tools:
> >
> >       - 13, 15, 17 and 19 mm sockets and open-end wrenches.
> >       - U-joint extension is very helpful but not essential.
> >       - Set of long handled metric Allen keys or hex bit sockets.
> >       - Bench vise and jaw protectors or a couple of pieces of wood.
> >       - Hand-operated siphon (cheap plastic thingy) and turkey baster.
> >       - 3/4" drag-link socket for 1/2" drive, available from
> >         professional tools suppliers (Snap-On, MacTools)
> >       - 1/2" hand impact drive (any h/w store -- mine from Home Depot).
> >       - Hammer.
> >
> >       Parts:
> >
> >       - O-ring repair kit (about $20.00 from Carlsen, but I paid
> >       more to Blaufergnuegen instead :-()
> >       - 2 litres of "Ol fur zentralhydraulik ..", CHF 7.1 or 11s 

** See ADDENDUM below

> >       Procedure:
> >
> >       1. Drain hydraulic reservoir with siphon.
> >
> >       2. Disconnect hoses connected with three banjo nuts to
> >       the pump (all three are different sizes). The front-most
> >       hose is also anchored to the rear of the pump with two
> >       bolts. At this point you can move all but the front-most
> >       hose out of the way (on the 3B engine .. disregard for
> >       older I-5's).
> >
> >       3. Drain as much oil from the pump as possible using the
> >       baster (to minimize the amount of oil on your garage floor).
> >
> >       4. Loosen top mounting bolt (about which the pump swings), then
> >       the hard-to-reach nut on the tensioning bracket (I used two
> >       extensions on my drive), and then the main tension adjusting
> >       bolt (U-joint extension really useful for this -- the axis
> >       is very close to the radiator housing). Remove the tension adjusting
> >       bolt and then the threaded fitting into which it goes.
> >
> >       5. Slip belt off pulley, and swing pump enough to work the front
> >       hose end out from under the pump mounting collar. (Applies only
> >       to 3B engine).
> >
> >       6. Remove the last mounting bolt and lift pump out (rotate clockwise
> >       and lift out vertically on the 3B).
> >
> >       7. Clamp the pulley in the vise (use protectors) and remove the pulley
> >       bolts. Then remove the four bolts (two Allen head, two regular) holding
> >       the mounting collar to the pump.
> >
> >       8. Clamp the pump in the vise and remove the two long Allen head bolts
> >       that hold the two halves of the pump together. They're torqued down
> >       quite tight, but come out easily once they break loose.
> >
> >       9. Replace the 6 (?) little O-rings and the big middle one. There were
> >       little black pieces of crud in the O-ring channels in mine: I swabbed
> > it
> >       clean with Q-tips. The O-rings must be coated with mineral oil before
> >       installation.
> >
> >       10. Remove the two check-valves (hex key, pretty tight) and replace the
> >       O-rings.
> >
> >       11. Bolt the two halves back together, and prepare to do the cap seals.
> >
> >       12. Clamp the drag-link socket in the vise and file down the corners by
> >       1 mm on each side so that it fits the slot on the cap screws
> >       -- I tapered mine a little to match the shape of the slot.
> >       (This is actually pretty easy to do -- I had the impression that
> >       sockets were made of sterner stuff).
> >
> >       13. Clamp the pump in the vise, and do the cap seals one by one. The
> >       pump's very odd-shaped, so be careful when clamping it -- I had mine
> >       work loose a couple of times. (It would not be funny if that pump
> >       were to fall on your foot -- though you'd save your pump!). To remove
> >       the cap screw, use the impact driver with your custom drag link socket.
> >       For those of you who haven't used one before, you twist it as far as
> >       it will go counterclockwise and hit it with a hammer while doing so.
> >       You have to hit pretty hard, but it comes out by hand once it's loose.

ADDENDUM: Someone later remarked that it's a lot easier if you use bolts
in the mounting holes to clamp the pump in the vise, but I forget the
details.

> >
> >       14. Fit mounting collar and pulley, and then Mount pump back in the
> > car,
> >       but connect the hoses only after filling the pump with oil and
> >       rotating the pulley until oil comes out of the farthest port.
> >
> >       15. While reconnecting the front hose, it helps if you screw in the
> > rear
> >       mounting bolts loosely first.
> >
> >       16. On the 3B, there are two little metal fingers on which
> >       the pump drive belt can easily snag while tensioning the belt.
> >       Look carefully to make the belt isn't snagging before you
> >       start the engine (I shredded my belt by not doing so ...
> >       luckily the belt needed replacement anyway).
> >
> >       17. Refill reservoir with fluid, and start the car. Check for leaks,
> >       and rotate the wheel from lock to lock quickly several times to bleed.
> >       Make sure the reservoir stays topped up, and bleed until the air
> >       bubbles stop.
> >
> >       That should do it. I didn't do the shaft seal, but any shop with
> >       a hydraulic press should be able to do it for you.
> >
> >       The seals were in pretty bad shape on my car -- hard, and breaking up.
> >       I suspect that this was because some quick-lube place topped the
> >       reservoir up with the synthetic variant (CHF 11, green can w/ red cap)
> >       (lots of places don't know any better, as I found out the hard way).

ADDENDUM: Phil Rose recently did some extensive research on the topic,
and discovered that Audi silently changed the hydraulic fluid from CHF
7.1 (mineral) to CHF 11s (synthetic) without changing the part number
(G000 2000?) some time in MY 1988. So it's fine if you refill with
synthetic. Indeed, the two may be safely miscible as well.

> >
> >       -Arun
> >
> > --
> > Arun Rao
> > Pixar Animation Studios
> > Pt. Richmond, CA 94804
> > (510) 620-3526
> >