Vibration in (ABS?) brake pedal first 5 minutes

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René Hazejager
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Vibration in (ABS?) brake pedal first 5 minutes

Ungelesener Beitragvon René Hazejager » 10.05.2005, 17:12

Collegues,

I need some help! My S6Plus sometimes vibrates in the brake pedal when it has started. Just like an active ABS system. And then I get the warning signal with the 3 sounds and brake with exclamation mark in the middle: it means you have to stop and drive carefully to Audi. They cannot find the cause... After 3-5 min everything seem to be normal.

I plan to check my pressure in the hydraulic system and/or drive to the dealer when it actually occurs and hook it up to the computer. The pressure bomb is OK. I do not want to exchange the ABS-unit because this costs a fortune!

Is anyone aware of a possibilty to disable the ABS?

Thanks!
René
Amsterdam
Porsche 911S 1972
S6Plus 1996

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Marc Welsch
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Re: Vibration in (ABS?) brake pedal first 5 minutes

Ungelesener Beitragvon Marc Welsch » 10.05.2005, 17:51

René Hazejager hat geschrieben:I do not want to exchange the ABS-unit because this costs a fortune!


You know, that it is possible to get a used one for small money? That might be better, than driving a PLUS without ABS... :roll:
Schöne Inselgrüße Marc

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René Hazejager
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Ungelesener Beitragvon René Hazejager » 10.05.2005, 20:55

Marc,

This is only for diagnostic purposes! If the vibration disappears, it has to be a faulty ABS-unit. I'm reluctant to change something in the blind...

Thanks,
René.

P.S. Nice forum!
Porsche 911S 1972

S6Plus 1996

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Marc Welsch
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Ungelesener Beitragvon Marc Welsch » 11.05.2005, 09:03

I just looked at a big german Audi-forum for your question. It seems to be quiet often, that the ABS-sensors at the wheels doesn't work anymore. Untill now nobody had a broken ABS-unit at all...
Schöne Inselgrüße Marc

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René Hazejager
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Ungelesener Beitragvon René Hazejager » 11.05.2005, 09:41

Marc,

I very much appreciate your efforts! Exactly what the dealer here states. I will read out the error messages soon.

In case of: where can I buy a second hand ABS-unit?

Cheers!
René.
Porsche 911S 1972

S6Plus 1996

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Marc Welsch
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Ungelesener Beitragvon Marc Welsch » 11.05.2005, 10:51

For example here :arrow: www.autewo.de , that's not so far away from the border to the netherlands...
Schöne Inselgrüße Marc

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Roland Müller
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Ungelesener Beitragvon Roland Müller » 13.05.2005, 01:58

Hi

I'm verry interested in your insights to solve the Problem, because I fear it's the same on my car.

It's very seldom the case and I think specially then, if my wife drives the car. Probably it is, because she strokes the brake-pedal softer and more seldom, then I do..., but that's not scientific proven... :D

Anyway, like René does, I don't believe that the system doesn't work properly. After e few seconds and/or a step on the pedal, the Brake works and feels as usual...
"...und denkt daran, ein plus ist ultra"

Grüsse romulo

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Joe Klugmann
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Ungelesener Beitragvon Joe Klugmann » 13.05.2005, 11:43

I had the same problem at a audi 90 quattro from a friend, it was the abs sensor at the wheel, i change it and no more errors or problems.
Mit freundlichen Grüßen
Yours sincerely
Veuillez agréer mes salutations distinguées

Joe Klugmann
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René Hazejager
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Ungelesener Beitragvon René Hazejager » 13.05.2005, 14:28

Hi,

Thanks for the feedback. I discussed this problem yesterday at a reliable AUDI-dealer, results:

1. No errors in the computer (ABS 100% OK)
2. No sensors defective
3. doubts about the hydraulic system
4. doubts about the ABS-unit
5. Accumulator 100%
6. Maybe the return valve in the brake servo (low probability)

I can provoke the problem if I push the brake pedal 40x before starting (than for sure the bomb is empty). If I start again with a pressurized bomb, I very seldom get problems.

Why doubts on the ABS-unit? Because you can feel the vibration if you put your hand on the unit and my hydraulic system is DRY.

So the next step is: get a tube and connect this to the servo (remove the pressure switch) and measure the pressure. I believe this must be more than 80 bar. And it should be there in 2 secs if the bomb is empty. I cannot find a dealer with the appropiate diagnostic equipment.....I ended up at hydraulic circuit specialist 150km away!

I will let you know my results.

Does anybody have the emailadres of the guy in Munich 'von S6Teile/Schlachtung'?

Cheers!
René
Porsche 911S 1972

S6Plus 1996

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Marc Welsch
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Ungelesener Beitragvon Marc Welsch » 13.05.2005, 14:52

Schöne Inselgrüße Marc

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René Hazejager
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Ungelesener Beitragvon René Hazejager » 24.06.2005, 17:48

Hi all,

I need your help. I've checked the hydraulic system just now according picture in my first post. Those are the results:

Pressure meter connected onto brake servo (removed the switch). This special company fabricated in no time a tube with the right adapter.

Fired up the engine. This resulted in no pressure at all. Until I braked the pressure came up to 60 bar. After 10x braking the pressure dropped to 50 bar and suddenly to zero. This indicates the bomb pressure is 50 bar. This is OK.

Switched off the engine. Again at 50 bar (<10x braking) the pressure dropped quickly after this to zero.

We almost concluded that the pump was weak, but he requested me to fire up the engine again and heavily move the steering wheel. No difference (of course the two systems are separated!).

Suddenly after 30secs the pressure reached 147 bar! This looks better. Again I was able to get the pressure down by braking 30x.

Still vibrations in the system (you could feel this on the tube to the pressure meter) the first 10 secs.

I highly appreciate your inputs on this irritating and potentially dangerous problem.


Thank you.
René.
Porsche 911S 1972

S6Plus 1996

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René Hazejager
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Ungelesener Beitragvon René Hazejager » 24.06.2005, 18:37

Hi,

Just realized that the picture was somewhere else.
See below how we measured.

Thanks!
René.
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Porsche 911S 1972

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Roland Müller
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Ungelesener Beitragvon Roland Müller » 02.07.2005, 23:27

Hi René

...before a few days I drove another Plus, and I was very amazed, that that pedal-way wasn't as far as mine is.
And also the feeling when I pushed down the was pedal, was different to mine. I would exlain it that way. If I brake, it feels like a rubber which is a bit elastic, while by the other Plus the feeling was more harder.

Some of you go one to say: then ist air in your system and I must say, the feeling is really that kind. But there isn't! The last change of break-fluid was done not a long time ago and the system was properly bleeded.

So I ask me, isn't the problem although the main brake cylinder, which costs about 300 Euro.

What are your expiriences?
"...und denkt daran, ein plus ist ultra"

Grüsse romulo

Sebastian
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Ungelesener Beitragvon Sebastian » 03.07.2005, 11:19

I will buy an used Main-Brake-Cylinder in a few days and will install that in my PLUS and than we see, what differences we will see :wink:

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René Hazejager
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Next steps

Ungelesener Beitragvon René Hazejager » 03.07.2005, 12:20

Hi fellows,

Wednesday I will remove my brake servo (Bremsverstaerker). But I will check first this part on leakage: I will remove the return line and start the engine. No hydraulic fluid should come out (only a few drips...).

About elastic/rubber/spongy pedal, can also be worn/soft rubber sealings in the main brake cylinder or caliper.

I will let you know!
This is an irritating problem and potentially dangerous, so I repair this at any cost.

MFG,
René.
Du hast keine ausreichende Berechtigung, um die Dateianhänge dieses Beitrags anzusehen.
Porsche 911S 1972

S6Plus 1996


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