[s-cars] No Brakes!!! Still

[Fred Munro]

Hi Mike;

The pump has two circuits, one for the steering and one for the brake boost.

If your bomb is good, it either isn't getting the pressure from the pump or
the servo isn't turning the pressure into brake assist at the master
cylinder. If the red light is on, that is showing low pressure in the boost
circuit and the pump is the culprit. If the red light is off when you are
having this problem, the servo may be the problem.

HTH

Fred Munro
'94 S4


-----Original Message-----
From: Mike Platt [mailto:mplatt911 at yahoo.com]
Sent: June 26, 2003 8:30 AM
To: Fred Munro
Cc: Scar
Subject: RE: [s-cars] No Brakes!!! Still


Well, I did the servo leak test and all was well. Not
a drop, well ok one or two. I replaced the bomb last
night and still have little to no brakes. I drove
around for 10 minutes and still have a firm pedal for
about 1 inch and then had some brakes. A really
dangerous feeling.

Wondering if the pump may be causing some problems??
The power steering is perfect. Is the pump a two
circuit type? Maybe the pump outputs fine for the
powersteering but not for the brakes?? The pump was
rebuilt a year ago.
I also cleaned out the filter in the tank and the two
bolts w/filters for the line from pump to accumulator.
They were fine anyway.

Ok whats next listers? You never let me down.
Thanks
Mike (loving spending all this cash on hydraulics) P.
95.5 S6 avant
+ 2 other P cars with no hyudraulic trash.

--- Fred Munro <munrof at sympatico.ca> wrote:
> Hi Mike;
>
> Your symptoms are typical of a discharged bomb. From
> your description, I
> suspect the following:
>
> 1. Your brake servo is leaking fluid back to the
> reservoir (the pressure in
> the bomb bleeds off after 20 minutes at low pump RPM
> and it takes 5 minutes
> to build pressure to power assist your brakes)
> AND/OR
> 2. Your pump is not putting out pressure and/or your
> banjo bolt screens are
> plugged (it takes 5 minutes to build pressure to
> power assist your brakes).
>
> You could also have a dead bomb, but if the bomb is
> dead and everything else
> is OK, the system should pressurize the dead bomb
> fairly rapidly, you just
> don't have much reserve boost. You could, however,
> have a dead bomb AND a
> bad pump/servo.
>
> The servo leakage test is in the Bentley. I suggest
> you start with that. If
> the servo is bad, replace it and try the system
> again. If the servo is
> totally blown, the pump probably can't keep up with
> the bypass flow and
> can't pressurize the bomb.
>
> You are right, the car is too dangerous to drive in
> this condition.
>
> HTH
>
> Fred Munro
> '94 S4
>
> -----Original Message-----
> From: s-car-list-admin at audifans.com
> [mailto:s-car-list-admin at audifans.com]On Behalf Of
> Mike Platt
> Sent: June 18, 2003 9:36 AM
> To: Scar
> Subject: [s-cars] No Brakes!!!
>
>
> My hydraulic woes seem to never end. On the way to
> work this morning I was caught in a traffic jam.
> After
> about 20 minutes of stop and go traffic, I started
> to
> lose my power assist, brakes only. I feel a
> pulsation
> from the pedal when I sit at idle so I think that
> the
> pump is fine. After about 5 minutes of freeway
> driving, I have power brakes for one stop and I am
> back to no power assist again. Very Dangerous
> feeling,
> I might add. I replaced pump last year, as well as,
> a
> recharged Bomb. I also flushed the entire system and
> use the new Pentosin 11s.
>
> Where should I be looking? Bomb or Power Brake
> booster?
> Guess this take priority over the idle and cruise
> control problems I am having.
>
> Thanks, hoping list bails me out again.
>
> =====
> Mike P
> 95.5 S6 avant
> 75 911 Carrera targa
> 74 914 2.0
> 99 Ducati ST4
>
>
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