Asking for opinions

[Huw Powell]

On 7/17/2010 12:42 AM, Johnny B wrote:
>
> Hmm, this seems like a vacuum related issue, jabbing the pedal would
> cause a surge in vacuum pressure making a weak failing part leak at a
> quicker rate then when slowly building the pressure in the system
> (depending ont he nature of the failure).

That makes no sense.  "Vacuum" is generated in the intake tract, and 
"stored" in the booster.  No vacuum "builds", it just gets used.

> Vac leak check is easy. Take a can of B12 Chemtool (or carb cleaner)
> and spray down the booster area&  all connections&  ports while the
> car is idling. If there is a leak the cars idle will adjust
> (increasing) for a bit. Remember chem tool&  carb cleaner is
> flammable so be conscious of that.

The only place a leak could matter would be inside the booster canister. 
  How is he supposed to get the flammable gas in there to test it?

>> Guys,
>>
>> I thought I'd put this out and see what others think.  The subject
>> is my 1980 Audi 5000S (type 43).  Its always had this little quirk
>> where braking power seems inverse to applied force.  If you stomp
>> on the brakes, you get very little assist.  However, if you step on
>> the brake pedal and apply increasing force, you get all the braking
>> you desire.
>>
>> When I first got this car (1986, my first Audi years ago!) it had
>> this symptom.  It had the Teves calipers on it, so I upgraded to
>> the Girling G54 calipers and 280MM rotor from the T5000 turbos of
>> that era.  I also have the rear disc brakes from the same.  Made no
>> difference in the brake function.
>>
>> My thought is that its something to do with the vacuum booster.
>> The standard test is to depress the pedal slightly and start the
>> engine and the pedal will pull in as vacuum builds and it does
>> that.  But I never been completely happy with this syndrome and was
>> wondering if its worth it to replace the vacuum booster.
>>
>> TIA,
>>
>> Tony
>>
>> '80 5000S '83 ur-quattro '87.5 coupe GT Special Build '01 A4 Avant
>> quattro 2.8
>>
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-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/