Re: bomb recharge procedure???

["Scott M." <scottmo@teleport.com>]

Mike,

I have not been following this bomb thread too closely but
has anyone discussed the other possible failure modes of
the pressure accumulator?

There is a internal check valve in the bomb where the high
pressure feed line comes in and there is also an internal 
pressure relief valve where the rubber return line connects
to the bomb, it returns excess fluid back to the reservoir
when the pressure gets above 150bar. (2175 psi)

I suspect that some bombs fail as a result of either one of
these two valves getting some crap (rubber hose fragments?)
in them which prevents them from sealing correctly. Failure
of either check valve would allow fluid to bleed back to
the reservoir or to back to the outlet at the pump. I
believe there are screens in the banjo bolts on some models
to help keep crud from getting in the bomb. 

When I buy a used Audi I like to remove the power
steering/brake fluid reservoir and clean out all the black
sludge that accumulates and then flush out the system with
new Pentosin by removing the return lines that go into the
reservoir and letting that fluid flow into a waste can
while the engine is running. It takes very little time for
the pump to send fluid back to the return lines so work
fast! You can also pump the brake pedal to get some fluid
flowing back from the brake power assist unit.

It would be interesting to dissect one of these bombs  and
get a look inside and see specifically why they fail over
time. 

Let us know what you find out.

Cheers
Scott M.