[urq] bomb test variation with S4 brakes?

brady zq bradyzq at hotmail.com
Tue Aug 8 12:06:48 EDT 2006

That would be me.

I get 10-12 pumps from as fully charged a bomb as I can get.

On ymy early 83 urq with twin piston G60's, urS4 rears, and braided 
stainless lines, orignial equipment MC, and new bomb, my pedal travel is now 
and has always been pretty short and firm. The only time it is mushy is when 
I do the bomb test with the engine off.

One thing I should mention, and this is not new (as in it occurred before 
the bomb switch and still does) is that I sometimes hear a "hissing" noise 
from the area of the brake pedal accompanied by very faint feeling change in 
the pedal. This happens when I have already stopped for a traffic light or 
something, after light braking, but with my foot on the brake pedal lightly 
to keep the car  from rolling. No moisture is evident form this. It's almost 
as if the bomb is refilling loudly. The noise is not coming from the pump. 
It's much closer than that.

And I don't have cruise control, so it's not likely to be venting vacuum at 
the brake pedal.

Any ideas?


>From: "Buchholz, Steven" <Steven.Buchholz at kla-tencor.com>
>... I don't recall anyone saying that it did.  Someone expressed concern 
>that their brand new PA was faulty because they weren't getting the 
>expected number of assisted pedal applications when the engine was shut 
>off.  My point was only that *if for some reason* you have longer pedal 
>travel than Audi originally planned for when they designed the system that 
>you might well expect the bomb will support fewer brake applications fewer 
>pedal depressions.
>Steve B
>San José, CA (USA)
> >
> > 1. I don't see how the bomb is going to change the pedal travel.

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