[s-cars] Brake/Power steering system drama-

Wed Nov 21 11:41:33 PST 2007

thanks Fred,

Im simply trying to flush the whole system as completely as possible after I
replace the pump.

thanks for you words, brian.

On 11/20/07, Fred Munro <munrof at sympatico.ca> wrote:
>
>  Brian;
>
> I think any of the banjo bolts can contain screens. I've seen them in the
> bolts on the pump.
>
> The top line on the servo is the return line to the reservoir. When the
> brake pedal is depressed, fluid flows through the servo and back to the
> reservoir through this line. If the servo is OK, you can remove the line and
> only a few drops of fluid should leak out (with the brake pedal NOT
> depressed and the system pressurized). If the servo is shot, fluid will flow
> through this port even if the brake pedal isn't depressed. This is one way
> the bomb can lose pressure once the engine is shut off.
>
> If you want to purge the servo using the top port, a standard metric brake
> line and fitting will thread into the port. You can attach a plastic hose to
> the brake line and lead it into a bottle. Pumping the brakes with the engine
> running will transfer fluid from the reservoir into the bottle. Actually,
> this is how I test the servo - if fluid flows through the line with the
> engine running and the brake pedal not depressed, the servo is shot. You may
> want to test the servo if you've had ATF in the system.
>
> HTH
>
> Fred
>
> -----Original Message-----
> *From:* brian hoeft [mailto:qweblog at gmail.com]
> *Sent:* November 20, 2007 12:43 PM
> *To:* Fred Munro
> *Cc:* brian bilotti; s-car-list at audifans.com
> *Subject:* Re: [s-cars] Brake/Power steering system drama-
>
> Fred, when you suggest removing the banjo bolts to purge the
> system/screens with the car off are you referring to 2 on the rack itself or
> all, like the one at the bomb too?
>
> Also, If the 12 o clock line on the servo were removed (after pumping to
> depressurize) before starting the car, wouldnt the system purge itself that
> way as well, so long as the reservoir still pulled in new fluid?
>
> ..Im having to replace my pump in the near future from my cross country
> line failure & ATF emergency fluid use and want to get all the red stuff out
> as best as possible..
>
> Thanks, brian
>
>
>
> On 11/19/07, Fred Munro <munrof at sympatico.ca> wrote:
> >
> > Brian;
> >
> > The steering and brake systems are independent to a certain extent but
> > they
> > use a common fluid reservoir and pump. The pump has two circuits; a high
> >
> > pressure low volume section for the brake assist and a low pressure high
> > volume section for the steering.
> >
> > The light on and the hard brake pedal indicates you have low pressure in
> > the
> > brake boost circuit and therefore little or no brake assist. The car is
> > dangerous to drive in this condition as it cannot be stopped easily
> > without
> > brake assist (as I'm sure you've found out).
> >
> > The system as installed is quite reliable when operating properly. It
> > would
> > be much easier to sort out the hydraulic boost system than to cobble
> > together something else. Some of the older non-turbo cars (coupes,
> > 4000's,
> > 100) that you mention in your post use a vacuum brake boost system that
> > takes it's vacuum from the intake manifold. That would work fine until
> > the
> > turbo kicked in and pressurized the manifold, hence the hydraulic system
> > on
> > the turbo cars.
> >
> > First of all, your "bomb" (hydraulic accumulator) is not holding
> > pressure.
> > With the engine off, fluid is leaking out of the bomb and back into the
> > reservoir. You can confirm this by looking at the reservoir level with
> > the
> > engine running and the light out and checking the level again after the
> > car
> > sits overnight. If the level rises overnight, the bomb is leaking back
> > into
> > the reservoir. This can be caused by a bad check valve in the bomb or a
> > leaking servo.
> >
> > When you start up the car and get the light and a hard brake pedal, that
> >
> > tells you that there is no stored pressure in the bomb to boost the
> > brakes.
> > The fact that the light stays on for a long time and the pedal stays
> > hard
> > tells me that the pump isn't pressurizing the circuit enough to boost
> > the
> > brakes. Usually with a dead bomb and good servo the pump will build
> > enough
> > pressure to give you easy braking for an "average" stop but not enough
> > for a
> > panic stop. When you stop and give the pedal some "serious pushing" you
> > are
> > pulsing the servo. Since this resolves the problem I suspect you have a
> > servo issue, probably hose debris clogging the internals. The servo is
> > probably leaking by so much that the pump can't pressurize the circuit.
> > After you pulse it, it stops leaking by and allows pressure to build in
> > the
> > boost circuit. You can check this by doing a leak-by test on the servo.
> >
> > I'd start by draining the hydraulic fluid, pulling all the banjo bolts
> > to
> > clean the internal screens, and pulling and cleaning the screen in the
> > reservoir. Turn the wheels side to side (with the engine OFF) to force
> > the
> > old oil out of the rack. Remove the reservoir and clean it out. Refill
> > with
> > new oil and try it again. If this doesn't work and the servo fails the
> > leak-by test, you'll need a new servo. No problem, they only cost $800
> > *cough, cough*
> >
> > HTH
> >
> > Fred Munro
> > '97 S6 (mit new servo)
> >
> > -----Original Message-----
> > From: s-car-list-bounces at audifans.com
> > [mailto:s-car-list-bounces at audifans.com ]On Behalf Of brian bilotti
> > Sent: November 19, 2007 12:45 AM
> > To: s-car-list at audifans.com
> > Subject: [s-cars] Brake/Power steering system drama-
> >
> >
> > S-Heads,
> > If you'll recall, awhile back I had the J hose blow.
> > Got it fixed at Pirtek, fast forward it blew again.
> > They fixed it.
> > Now on start up and for quite awhile the brake light
> > stays on and the brake pedal is extremely hard to
> > press. I end up pulling over and give the pedal some
> > serious pushing to force it down. Drive a little bit,
> > light goes off and everything's fine.
> > I'm really sick of this BS.....
> >
> > Two questions:
> >
> > 1. Any ideas WTF this is?
> >
> > 2. Anybody change their brake system so the two
> > systems are independant of each other?
> >
> > Javad has done it for the coupes and 4000 I think, but
> > he can't do it for the Urs. Another buddy of mine says
> > that a brake booster off a 100 and some other Audi
> > parts (my mind is blank on that one, maybe a master
> > cylinder) he seems to think this is a viable
> > project.... That said, I wanna ask if there's been any
> > BTDT out there.
> >
> > Lemme know
> >
> > Brian
> >
> >
> >
> > ______________________________________________________________________
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>
>
>
> --
> ====
> ! beat the NWO cult ! www.RonPaul2008.com <http://www.ronpaul2008.com/>|
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> //brian
>
>

-- 
====
! beat the NWO cult ! www.RonPaul2008.com |  www.BWAnetwork.com/home
www.humanhealth.wholefoodfarmacy.com | and be proud of my allies at
>> www.hourofthetime.com

//brian