[urq] Correct "technical" name for hydraulic part

Tue Jul 19 18:02:59 EDT 2005

Guys, thanks for the replies. I've studied the mentioned pages and tried to 
figure out which (faulty) part of the Flow Regulator could cause my problems 
with the delayed brakes and pedal feeling and noises, summarized below:

Replaced parts:

Brake Master Cylinder (OE)
Proportioning Valve (OE)
Brake Accumulator aka "bomb" (FEBI - BMW)
Pressure bled several times with fresh fluid.

Checked:

ATF level = OK (half full)
DOT4 level = OK
Brake Servo for internal leakage = OK
Pressure switches inside Flow Regulator = OK (ohm test per Phil Payne's 
website) autocheck system = OK)

Current situations:

A) While stationary and running engine, pedal moves in "2 steps" to the 
floor after ~30% travel but not "easy" like when air is trapped inside. When 
this happens you hear a strange zooming noise and the same time a fast 
ticking noise, which is also "felt" if you touch/hold the large high 
pressure line from the Flow Regulator to the Brake Servo. You can hear that 
ticking noise also when the pedal is pushed gently (feather), or turning the 
wheel, both stationary and whilst driving.

B) While driving the pedal/brakes feel absolutely normal if applied slowly 
(except for the ticking noise).

C) When applied real hard and fast (i.e. panic stop), the pedal feels 
initially hard and with delayed (1-2 sec) response. Same feeling if I take 
off fast (high revs) and then quickly apply the brakes: initially nothing, 
then full stop (because of the extra foot pressure applied).

D) Turning off the ignition while driving at 60km/h leaves enough 
"emergency" brake assistance for one application only and even some steering 
assistance. After a complete stand still, the pedal feels rock hard like a 
"empty" bomb should. I've tried this several times and managed to lock the 
front wheels quiet easily when ABS is switched off, and engaged ABS when 
switched on.

E) When the engine is off, the pedal feels quite normal but by no means 
"rock-hard" like it does after the D) mentioned test.
Even after 60+ applications (w/engine off), it still feels the same. The 
bomb just won't empty (ATF level does not rise, all I can see inside the 
container is fluid that looks like it's been shaken, no longer 
red-crystal-clear if you know what I mean, I'm not shure it looks like mixed 
air, perhaps it's nitrogen?

I'll take it that:

The new bomb appears to be OK considering the 60+ applications and the 
sufficient emergency assistance -if one brake app. is called sufficient.
BMC and PV should be OK considering they're new.
Brake servo does not leak internally (24h test).
No air and no soft but "normal" pedal feeling when engine is off and it's 
also possible to lock the wheels with ABS turned off if that means anything.

My million dollar questions:

1) When the pedal is pushed down in situation A), where does the brake fluid 
go if there is no air trapped inside (E), or is there?

2) Theoretically, in what position should the non-return valve inside the 
Flow Regulator stick when the brakes feel normal if pushed gently/slowly and 
not when pushed hard/fast if the bomb is OK?

3) If the cut-off valve inside the FR is sticking in the "pressurized" pos. 
while it's not, could this prevent the bomb from being emptied while in fact 
it is pressurized?

4) If the bomb is faulty or not able to be pressurized completely, say only 
up to 40 bar like an old bomb (symptom of situation C) and perhaps E because 
there is no fluid flowing), why does it apply enough emergency assistance 
for at least one application and tested negative for the bomb test in E)?

5) How many emergency brake applications/assistance should a good system 
with new bomb supply, mentioned in D)?

Any new insights or suggestions are highly appreciated... (I'm sorry I keep 
on posting the same problem over and over again).

Regards,
Maurits

1986 GV (Swiss WR)
1985 CGT KV
1982 GL DD

----- Original Message ----- 
From: "Tony Lum" <tlum at flash.net>
To: "Maurits Jonkergouw" <urq at moregraphics.nl>; <urq at audifans.com>
Sent: Tuesday, July 19, 2005 4:52 PM
Subject: Re: [urq] Correct "technical" name for hydraulic part

At 11:27 AM 7/19/2005 +0200, Maurits Jonkergouw wrote:

>What is the correct technical name for the "valve block" P/N 857 612 063 A
>- this is where the (WR) brake accumulator, aka bomb houses -
>
>Unfortunately many people refer to "brake pressure regulator" when they
>mean "proportioning valve" and this widly extends my search results on the
>Audifans archive...
>
>I would like know if the mentioned "valve block" could be rebuilded
>because the dealer quotes a HUGE amount of money for it.
>
>Thanks
>--
>.................................................................
>Regards,
>Maurits
>.................................................................
>'86 quattro GV (WR)
>'85 coupé KV
>'82 coupé DD
>.................................................................

Hi Maurits,

Page 42 of the IST document (WSP 451 556 00) refers to it as a "Flow
regulator with Pressure accumulator".  Pages 44, 48 and 49 give a detailed
description of operation.  From the looks of it, you could possibly rebuild
it if you can disassemble it and find all the O rings that seal the various
chambers.  Perhaps a good cleaning will restore its function.  If not, you
might consider switching to a vacuum assist unit from coupe GT or others.

HTH,

Tony
'83 urq #302

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