[s-cars] bomb time

[Tom Green]

The classic bomb problem is the failure to retain system pressure when  
the engine is shut off.  This shows itself as the brake light  
remaining on after start for ~30 seconds.  That is the only function  
of the accumulator-retain sufficient brake pressure for emergency use  
when the engine is off.   When the engine is running and the pump has  
had time to charge the bomb to full system pressure, it does not  
really come into play unless you make very high demands that the pump  
can't supply and/or there is some other problem as well. So, you may  
need a bomb, but probably something else as well.

That could be a system flush and filter cleaning or some more  
hardware.  Check out the FAQ at the UrS4/6/S2/RS2 forum on  
Quattroworld.com then don't ask questions until you have looked  
here.  : )   If the light is on at every start, probably plan on a  
bomb, but start by looking at the fluid in the hydraulic reservoir.   
Check for a bright, clear olive green color;  pull the little plastic  
sleeve with the screen that drops in the reservoir fill hole.  The  
screen should be bright steel.  If it is black, that is rubber from  
seals and hoses.  Black fluid and filter means cleaning and flushing  
is overdue.  I recommend putting a 3/8" Magnefine filter in the return  
line also.  I would do this cleaning/flushing/fluid change before  
deciding what is broken from the troubleshooting discussed below.  It  
could just be junk blocking flow through the screens in the banjo  
bolts or reservoir and/or keeping a check valve in the bomb or servo  
from closing fully.

The only problem with this troubleshooting procedure is without a  
pressure test on the pump output to the brakes, you don't know if a  
weak pump output is causing or at least contributing to the problem.   
If the servo leaks, that could be the only problem, but you can't  
really tell if the system won't hold pressure so you can test the  
other parts.  An extra part or two would be no big deal for a system  
that has this age on it, but these are expensive parts.

This is the place to start in the FAQ:

http://members.shaw.ca/speedtek/UrS%20chassis%20Map.html

And, this is the section to troubleshoot your system to determine  
where to start, and it is not go buy a bomb:

http://www.elektro.com/~audi/audi/hydraulic.html


Here is another source for accumulators;  Unfortunately, he is out of  
stock:

PARTS FOR AUDI C4 CARS (100 / S4 / A6 / S6 & S6 PLUS)

The squealing brake is a brake problem, not a hydraulic boost problem.


Cheers,

  Tom '95 S6
          '95.5 S6 avant
Knoxville, TN



OnSaturday January 21, 2012, at 1:05 PM, "Steve Marinello" <smarinello at entouch.net 
 > wrote:

> I expect to be needing a new bomb shortly, as the light now comes on
> at.interesting times.  One observation.when it comes on during  
> braking from
> relatively slow speeds, the brakes squeak.reduced clamping force?   
> I'll
> check to see if Dave Kase is still recharging them, but I was  
> wondering if
> anyone knows much about where the new ones are being made.  WOrldPac  
> has
> Febi Bilstein bombs and there are a couple of sources with Meyle  
> units,
> including GR on ebay.  I'm guessing the Meyle ones are definitely  
> Chinese
> now; anyone know about the Febi's?  There's about a $45-$50 price
> differential.
>
>
>
> TIA,
>
>
>
> Steve
>