[s-cars] Brake Light and Thrumming Pedal

Sun Jul 2 16:16:12 EDT 2006

OK, I'll check.  Here is my other question for the day.  How in blazes
to you get the fitting on the return line off?  I can't find clearance
for my 11 mm brake fitting wrench.  I can get a cheap 11 mm stubby on
there, but it didn't want to budge and I am afraid of using too much
force with that wrench and stripping the hex head on the fitting.

I am leary of using penetrating oil in this application.

Any suggestions?

D.

On 7/2/06, brian hoeft <qweblog at gmail.com> wrote:
>
> that same NAPA should sell a tube bender,the guys at the counter might know
> it better for bending brake lines.. looks kind of like a hockey stick w/a
> groove to hold the line in place.
>
> should be just a few bucks for the one you'll need.
>
> good luck, //brian
>
>
>
> On 7/1/06, Douglas Fifield <douglas.fifield at gmail.com> wrote:
> > Fred,
> >
> > I just walked into the house from NAPA with an 8" section of metric
> > line.  Sounds just like what you describe.  Do you have advice on how
> > to bend it without kinking it?
> >
> > D.
> >
> > On 7/1/06, Fred Munro <munrof at sympatico.ca> wrote:
> > > Douglas;
> > >
> > > Ask for 3/16" European metric brake line. It will have the proper flare
> and nut.
> > >
> > > I've attached a photo of my test apparatus.
> > >
> > > Fred
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: Douglas Fifield [mailto: douglas.fifield at gmail.com]
> > > Sent: July 1, 2006 12:16 PM
> > > To: Fred Munro
> > > Cc: s-car-list at audifans.com
> > > Subject: Re: [s-cars] Brake Light and Thrumming Pedal
> > >
> > >
> > > All,
> > >
> > > So, if I want to test the servo as described and go to the FLAPS to
> > > get a piece of metric brake line, is there just one size of flanged
> > > fitting, or do I need to know the correct size?  If the latter, can
> > > someone supply that info?
> > >
> > > Douglas
> > >
> > > On 6/30/06, Fred Munro <munrof at sympatico.ca> wrote:
> > > > Douglas;
> > > >
> > > > If the level doesn't fall, the bomb is not being charged with fluid.
> This could be a really bad servo or a bad pump. At this point I'd do the
> servo test to rule that out. A totally dead bomb would also not draw fluid
> out of the reservoir, but it should allow the system to pressurize and the
> light would go out.
> > > >
> > > > I replaced the servo in a couple hours. You don't need to do a brake
> bleed - you remove the two bolts securing the master cylinder to the servo,
> release the brake lines to the MC from the multi-line clamp, and slide the
> MC off the servo without removing the brake lines. When the new servo is
> installed, you slide the MC back onto the servo and bolt it up. You don't
> have to open up the lines or bleed the brakes.
> > > >
> > > > As Brian mentioned, the servo is secured by four 13mm nuts that also
> secure the pedal cluster. The top left nut is a bit tricky as Brian points
> out, but I got it using 18" of 1/4" drive extensions and a flex end. You
> have to use 1/4" drive stuff or you can't see past the extensions to the
> nut. You have to use multiple extensions and assemble them as you insert
> them through the hole in the pedal cluster. Remember to get a new sponge
> gasket to seal the servo to the firewall. Unfortunately I didn't do a
> write-up on this.
> > > >
> > > > Hopefully you don't need a servo, but the alternative is probably the
> pump. If the servo tests good, you'll have to make up a pressure testing rig
> or take the car to the dealer to test the pump output pressure.
> > > >
> > > > HTH
> > > >
> > > > Fred
> > > >
> > > > -----Original Message-----
> > > > From: Douglas Fifield [mailto:douglas.fifield at gmail.com ]
> > > > Sent: June 30, 2006 11:07 AM
> > > > To: Fred Munro
> > > > Cc: s-car-list at audifans.com
> > > > Subject: Re: [s-cars] Brake Light and Thrumming Pedal
> > > >
> > > >
> > > > Fred and Everyone Else,
> > > >
> > > > Pushed the car out of the garage this morning, raised hood, had #1 son
> > > > start engine while I watched G002000 level in resivoir.  It was above
> > > > the full mark at about the seam level around the top of the tank.  It
> > > > did not move discernably the whole time the engine was running.  Brake
> > > > light was on and brake pedal thrumming.  Turned engine off and brake
> > > > pedal was rock hard.  Resivoir level never changed.
> > > >
> > > > What does this tell us?  I will try to find the materials to do the
> > > > servo leak test, but I don't have those materials readily available.
> > > >
> > > > D.
> > > >
> > > > On 6/29/06, Fred Munro <munrof at sympatico.ca> wrote:
> > > > > Douglas;
> > > > >
> > > > > Do the reservoir drawdown test I detailed in my earlier post. If the
> bomb is OK and the servo is leaking, the pump will partially charge the bomb
> and pull oil out of the reservoir with the engine running. Once you stop the
> engine, the oil will leak back out of the bomb through the servo and fill up
> the reservoir. If this happens, you'll have to test the servo to isolate it
> as the cause. This leak will be too large to do the Bentley servo test. You
> should use a test rig similar to what I described.
> > > > >
> > > > > If the bomb has failed, the pump will not put much oil into it and
> the level in the reservoir won't change much.
> > > > >
> > > > > Fred
> > > > >
> > > > >
> > > > >
> > > > > -----Original Message-----
> > > > > From: Douglas Fifield [mailto:douglas.fifield at gmail.com]
> > > > > Sent: June 29, 2006 4:24 PM
> > > > > To: Fred Munro
> > > > > Cc: s-car-list at audifans.com
> > > > > Subject: Re: [s-cars] Brake Light and Thrumming Pedal
> > > > >
> > > > >
> > > > > Fred et al,
> > > > >
> > > > > Things have progressed on the brake problem front.  Now, as soon as
> I
> > > > > turn off the engine, the brake pedal goes rock hard.
> > > > >
> > > > > I am not sure if this means the bomb has failed, or if the servo is
> > > > > leaking so badly that the bomb cannot be pressurized.
> > > > >
> > > > > Any thoughts?
> > > > >
> > > > > D.
> > > > >
> > > > >
> > > > > On 6/28/06, Fred Munro <munrof at sympatico.ca> wrote:
> > > > > > Douglas;
> > > > > >
> > > > > > The bomb has depressurized overnight. The brake light is on to
> warn of low
> > > > > > pressure in the brake boost system. The thrumming brake pedal is
> caused by
> > > > > > the pressure pulses from the positive displacement hydraulic pump.
> When you
> > > > > > apply the brakes with no stored pressure in the bomb, the boost
> pressure
> > > > > > comes from the pump and you feel the high and low pressure pulses
> as
> > > > > > vibration in the brake pedal.
> > > > > >
> > > > > > The bomb discharges due to a leaking check valve in the bomb or a
> leaking
> > > > > > brake servo. I used to believe the bomb check valve was the usual
> culprit,
> > > > > > but I now suspect the servo is usually at fault. The servo can
> leak by so
> > > > > > badly that the pump will never built up enough pressure to turn
> off the
> > > > > > warning light - I just had this problem in my '97 S6. If your
> warning light
> > > > > > doesn't go off, this is most likely your problem. A bad bomb check
> valve
> > > > > > will not prevent the bomb from pressurizing to design pressure.
> > > > > >
> > > > > > Flushing the central hydraulic fluid sometimes corrects the
> problem. Clean
> > > > > > the strainer in the reservoir when you flush the fluid.
> > > > > >
> > > > > > You can determine if you have a bad servo or check valve leak by
> running the
> > > > > > engine and noting the level in the reservoir. Shut off the engine
> and watch
> > > > > > the level. If you can see it visibly rising, either the servo is
> toast or
> > > > > > the bomb check valve is leaking badly. To test the servo, run the
> engine to
> > > > > > charge the bomb. Stop the engine. Remove the RETURN line on the
> servo (the
> > > > > > top connection). If more than a few drops of oil leaks out, the
> servo is
> > > > > > kaput. If you can see the fluid level rise in the reservoir, this
> test is
> > > > > > not a good one for two reasons:
> > > > > > 1. By the time you get the return line off, all the pressure has
> leaked out
> > > > > > and no oil will be released.
> > > > > > 2. If you do get the line off in time, so much oil will come out
> you'll have
> > > > > > it all over the rack and the driveway.
> > > > > >
> > > > > > I built a test rig to test my servo. I discharged the bomb
> completely by
> > > > > > pumping the brakes and removed the servo return line. I clamped
> off the
> > > > > > rubber section of the return line with a brake hose clamp. I bent
> a 8"
> > > > > > section of pre-made metric brake line at 90 degrees and threaded
> one end
> > > > > > into the return line port. I attached a plastic hose on the other
> end and
> > > > > > ran the hose into a jar. Start the engine (do NOT apply the
> brakes!!!) and
> > > > > > watch the plastic line. A flow of oil indicates a leaking servo.
> On the '97
> > > > > > the oil flow was a steady stream - the servo was completely shot.
> Funny, the
> > > > > > car had just been certified too. That explained why the warning
> light was
> > > > > > disconnected......
> > > > > >
> > > > > > HTH
> > > > > >
> > > > > > Fred Munro
> > > > > > '97 S6
> > > > > > '94 S4
> > > > > >
> > > > > > -----Original Message-----
> > > > > > From: s-car-list-bounces at audifans.com
> > > > > > [mailto:s-car-list-bounces at audifans.com]On Behalf Of Douglas
> Fifield
> > > > > > Sent: June 28, 2006 9:27 PM
> > > > > > To: s-car-list at audifans.com
> > > > > > Subject: [s-cars] Brake Light and Thrumming Pedal
> > > > > >
> > > > > >
> > > > > > Hedz,
> > > > > >
> > > > > > We have been over this one before, but I keep hoping that someone
> will
> > > > > > have figured it out and give me a clue.
> > > > > >
> > > > > > On and off, my S6 has had periods where the brake light stays on
> > > > > > beyond the normal 20 or so seconds in the morning.  These sessions
> > > > > > have been accompaning by a thrumming brake pedal and as long as
> that
> > > > > > continues, the brake light stays on.  In the past, the thrumming
> would
> > > > > > eventually stop and a few seconds later, the light would go out.
> > > > > > Today, it stayed with me and now the car is in the garage.
> > > > > >
> > > > > > It seems to stop normally.  Just had the brakes flushed last week
> and
> > > > > > the fluid levels are good.
> > > > > >
> > > > > > Any ideas?
> > > > > >
> > > > > > --
> > > > > > Douglas in MN
> > > > > > 95.5 Audi S//6 Avant
> > > > > > 73 BMW R60/5 mit Toaster Tank
> > > > > > _______________________________________________
> > > > > > S-CAR-List mailing list
> > > > > > S-CAR-List at audifans.com
> > > > > >
> http://www.audifans.com/mailman/listinfo/s-car-list
> > > > > >
> > > > > >
> > > > >
> > > > >
> > > > > --
> > > > > Douglas in MN
> > > > > 95.5 Audi S//6 Avant
> > > > > 73 BMW R60/5 mit Toaster Tank
> > > > >
> > > > >
> > > >
> > > >
> > > > --
> > > > Douglas in MN
> > > > 95.5 Audi S//6 Avant
> > > > 73 BMW R60/5 mit Toaster Tank
> > > >
> > > >
> > >
> > >
> > > --
> > > Douglas in MN
> > > 95.5 Audi S//6 Avant
> > > 73 BMW R60/5 mit Toaster Tank
> > >
> > >
> > >
> >
> >
> > --
> > Douglas in MN
> > 95.5 Audi S//6 Avant
> > 73 BMW R60/5 mit Toaster Tank
> > _______________________________________________
> > S-CAR-List mailing list
> > S-CAR-List at audifans.com
> > http://www.audifans.com/mailman/listinfo/s-car-list
> >
>
>

-- 
Douglas in MN
95.5 Audi S//6 Avant
73 BMW R60/5 mit Toaster Tank