1984 Audi 4000S Quattro brake bleeding
 

Hi,
I think there is air in my rear brake lines, but bleeding is a
rediculous pain. I know the proportioning valve on the '84 is not
adjustable, but is there a way to disable it? I know the first ones on
Jeeps there was a button that could be held. I just want a way to keep
normal pressure or lot's of pressure to the rears while bleeding.
Right now I can bleed once and then the rears get closed off.

My main problem is that I have either a leak or air in my lines, but I
can't see a leak and don't seem to lose fluid. If I press my brake
pedal slowly it goes about 3/4 or 7/8 to the floor, but still feels
like a normal pedal. When it does this I get pressure to all 4 wheels,
but probably about half of what I'd call normal pressure. If I push
the pedal more rapidly or fast it will only go half way and feel like a
normal pedal with full pressure, but only the front wheels will have
pressure. I'm hoping it's just air in the rear lines and under lots of
pressure that compressed enough to divert the flow and close off the
rears. If it's something more serious then maybe there's a way I can
make the fronts always have the pressure? Right now I can brake fine
with the mostly depressed pedal, I'm just worried when I go to get the
car inspected they will say it's inappropriate that way.

Thanks for any help,
Chris

Chris,
The brake system is supposed to be a closed system, so any air in the lines
or loss of pressure is a serious issue. On the proportioning valve, it's
supposed to reduce the pressure to the rears when the car brakes - as when
the nose dives - thus pulling on the spring which activates the valve. In
order to bleed the system, IIRC, you have to fool the prop. valve into
thinking that the car's suspension is at rest (some of the postings on
Audifans mention pulling the prop valve lever to the rear of the car). If
you don't trick the valve, you'll only have 20% of the brake pressure going
to the rear, and 80% to the front.
WRT the brake system, if you're using the original lines then you're asking
for trouble. Old lines can become herneated and collapsed internally and
you'd never see a problem until they burst. Check the hard lines for
excessive corrosion as well - you can get lengths of metric bubble flare
tubing at your local FLAPS. The difference between slow and fast presses of
the pedal sounds like brake fluid is bypassing the plunger in the master
cylinder. I have read postings where people have mentioned that the seals
in the MC get damaged while bleeding, as they pass along areas of the
cylinder that they wouldn't normally (and where some corrosion may exist)
when the pedal is pumped to the floor.
Brakes are something that should not be "mickey moused" - they're not
optional equipment. You need all 4 wheels to have them, not the fronts
only.
Cheers!
Steve Sears
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
(SPAM Blocker NOTE: Remove SHOES to reply)
> wrote in message
oups.com...
> Hi,
> I think there is air in my rear brake lines, but bleeding is a
> rediculous pain. I know the proportioning valve on the '84 is not
> adjustable, but is there a way to disable it? I know the first ones on
> Jeeps there was a button that could be held. I just want a way to keep
> normal pressure or lot's of pressure to the rears while bleeding.
> Right now I can bleed once and then the rears get closed off.
>
> My main problem is that I have either a leak or air in my lines, but I
> can't see a leak and don't seem to lose fluid. If I press my brake
> pedal slowly it goes about 3/4 or 7/8 to the floor, but still feels
> like a normal pedal. When it does this I get pressure to all 4 wheels,
> but probably about half of what I'd call normal pressure. If I push
> the pedal more rapidly or fast it will only go half way and feel like a
> normal pedal with full pressure, but only the front wheels will have
> pressure. I'm hoping it's just air in the rear lines and under lots of
> pressure that compressed enough to divert the flow and close off the
> rears. If it's something more serious then maybe there's a way I can
> make the fronts always have the pressure? Right now I can brake fine
> with the mostly depressed pedal, I'm just worried when I go to get the
> car inspected they will say it's inappropriate that way.
>
> Thanks for any help,
> Chris
>

I wish I had a spring or a lever. This is an '84. '85 to '87 used the
spring and lever to tell suspension diving and adjust accordingly, it
was an adjustable prop. valve. The '84 does not have this. My prop
valve is just below the master cylinder and completely unadjustable.
All of my brake lines are steel and seem to be in good order. I was
looking/hoping for that fooling pressure to the rear step you mentioned
but for an '84.

My brakes do work as per new if I push the pedal 'slowly' or whatnot,
I'm thinking when pushing fast it sense a rear leak and closes off
pressure. I suppose I should have been saying combination valve the
whole time instead of prop.valve.

Anyway, thanks for your help,
Chris

Steve Sears wrote:
> Chris,
> The brake system is supposed to be a closed system, so any air in the lines
> or loss of pressure is a serious issue. On the proportioning valve, it's
> supposed to reduce the pressure to the rears when the car brakes - as when
> the nose dives - thus pulling on the spring which activates the valve. In
> order to bleed the system, IIRC, you have to fool the prop. valve into
> thinking that the car's suspension is at rest (some of the postings on
> Audifans mention pulling the prop valve lever to the rear of the car). If
> you don't trick the valve, you'll only have 20% of the brake pressure going
> to the rear, and 80% to the front.
> WRT the brake system, if you're using the original lines then you're asking
> for trouble. Old lines can become herneated and collapsed internally and
> you'd never see a problem until they burst. Check the hard lines for
> excessive corrosion as well - you can get lengths of metric bubble flare
> tubing at your local FLAPS. The difference between slow and fast presses of
> the pedal sounds like brake fluid is bypassing the plunger in the master
> cylinder. I have read postings where people have mentioned that the seals
> in the MC get damaged while bleeding, as they pass along areas of the
> cylinder that they wouldn't normally (and where some corrosion may exist)
> when the pedal is pumped to the floor.
> Brakes are something that should not be "mickey moused" - they're not
> optional equipment. You need all 4 wheels to have them, not the fronts
> only.
> Cheers!
> Steve Sears
> 1987 Audi 5kTQ
> 1980 Audi 5k
> 1962 and '64 Auto Union DKW Junior deLuxes
> (SPAM Blocker NOTE: Remove SHOES to reply)
> > wrote in message
> oups.com...
> > Hi,
> > I think there is air in my rear brake lines, but bleeding is a
> > rediculous pain. I know the proportioning valve on the '84 is not
> > adjustable, but is there a way to disable it? I know the first ones on
> > Jeeps there was a button that could be held. I just want a way to keep
> > normal pressure or lot's of pressure to the rears while bleeding.
> > Right now I can bleed once and then the rears get closed off.
> >
> > My main problem is that I have either a leak or air in my lines, but I
> > can't see a leak and don't seem to lose fluid. If I press my brake
> > pedal slowly it goes about 3/4 or 7/8 to the floor, but still feels
> > like a normal pedal. When it does this I get pressure to all 4 wheels,
> > but probably about half of what I'd call normal pressure. If I push
> > the pedal more rapidly or fast it will only go half way and feel like a
> > normal pedal with full pressure, but only the front wheels will have
> > pressure. I'm hoping it's just air in the rear lines and under lots of
> > pressure that compressed enough to divert the flow and close off the
> > rears. If it's something more serious then maybe there's a way I can
> > make the fronts always have the pressure? Right now I can brake fine
> > with the mostly depressed pedal, I'm just worried when I go to get the
> > car inspected they will say it's inappropriate that way.
> >
> > Thanks for any help,
> > Chris
> >

Chris,
You might try asking the 4k people on Audiworld, or try Huw at
www.humanspeakers.com/audi
I have cc'd the q-list at Audifans to see if someone may be able to provide
assistance (q-listers, e-mail replies to Chris directly)
Cheers!
Steve Sears
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
(SPAM Blocker NOTE: Remove SHOES to reply)

> wrote in message
oups.com...
> I wish I had a spring or a lever. This is an '84. '85 to '87 used the
> spring and lever to tell suspension diving and adjust accordingly, it
> was an adjustable prop. valve. The '84 does not have this. My prop
> valve is just below the master cylinder and completely unadjustable.
> All of my brake lines are steel and seem to be in good order. I was
> looking/hoping for that fooling pressure to the rear step you mentioned
> but for an '84.
>
> My brakes do work as per new if I push the pedal 'slowly' or whatnot,
> I'm thinking when pushing fast it sense a rear leak and closes off
> pressure. I suppose I should have been saying combination valve the
> whole time instead of prop.valve.
>
> Anyway, thanks for your help,
> Chris
>
> Steve Sears wrote:
> > Chris,
> > The brake system is supposed to be a closed system, so any air in the
lines
> > or loss of pressure is a serious issue. On the proportioning valve,
it's
> > supposed to reduce the pressure to the rears when the car brakes - as
when
> > the nose dives - thus pulling on the spring which activates the valve.
In
> > order to bleed the system, IIRC, you have to fool the prop. valve into
> > thinking that the car's suspension is at rest (some of the postings on
> > Audifans mention pulling the prop valve lever to the rear of the car).
If
> > you don't trick the valve, you'll only have 20% of the brake pressure
going
> > to the rear, and 80% to the front.
> > WRT the brake system, if you're using the original lines then you're
asking
> > for trouble. Old lines can become herneated and collapsed internally
and
> > you'd never see a problem until they burst. Check the hard lines for
> > excessive corrosion as well - you can get lengths of metric bubble flare
> > tubing at your local FLAPS. The difference between slow and fast
presses of
> > the pedal sounds like brake fluid is bypassing the plunger in the master
> > cylinder. I have read postings where people have mentioned that the
seals
> > in the MC get damaged while bleeding, as they pass along areas of the
> > cylinder that they wouldn't normally (and where some corrosion may
exist)
> > when the pedal is pumped to the floor.
> > Brakes are something that should not be "mickey moused" - they're not
> > optional equipment. You need all 4 wheels to have them, not the fronts
> > only.
> > Cheers!
> > Steve Sears
> > 1987 Audi 5kTQ
> > 1980 Audi 5k
> > 1962 and '64 Auto Union DKW Junior deLuxes
> > (SPAM Blocker NOTE: Remove SHOES to reply)
> > > wrote in message
> > oups.com...
> > > Hi,
> > > I think there is air in my rear brake lines, but bleeding is a
> > > rediculous pain. I know the proportioning valve on the '84 is not
> > > adjustable, but is there a way to disable it? I know the first ones
on
> > > Jeeps there was a button that could be held. I just want a way to
keep
> > > normal pressure or lot's of pressure to the rears while bleeding.
> > > Right now I can bleed once and then the rears get closed off.
> > >
> > > My main problem is that I have either a leak or air in my lines, but I
> > > can't see a leak and don't seem to lose fluid. If I press my brake
> > > pedal slowly it goes about 3/4 or 7/8 to the floor, but still feels
> > > like a normal pedal. When it does this I get pressure to all 4
wheels,
> > > but probably about half of what I'd call normal pressure. If I push
> > > the pedal more rapidly or fast it will only go half way and feel like
a
> > > normal pedal with full pressure, but only the front wheels will have
> > > pressure. I'm hoping it's just air in the rear lines and under lots
of
> > > pressure that compressed enough to divert the flow and close off the
> > > rears. If it's something more serious then maybe there's a way I can
> > > make the fronts always have the pressure? Right now I can brake fine
> > > with the mostly depressed pedal, I'm just worried when I go to get the
> > > car inspected they will say it's inappropriate that way.
> > >
> > > Thanks for any help,
> > > Chris
> > >
>

1984 Audi 4000S Quattro brake bleeding
 

Do audi's require a different brake bleeding procedure after you replace
the master cylinder, I have a 1993 quattro 100cs and I'm having
problems. Any suggestions?


--
kevind1
------------------------------------------------------------------------
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View this thread: http://www.audiforum.ca/showthread.php?t=6543

1984 Audi 4000S Quattro brake bleeding
 

abs equipped?

Are you using a pressure bleeder? Or the old foot method?
What problems are you having?

If you are using the foot/ pressure bleeder method I recommend that you
bleed the master first by slightly opening 1 brake line at a time on the
master, pump if needed until you get a solid stream of fluid out, close off
that line. Do that with all of them and then bleed at the 4 corners
furthest away from the master. There might be a valve that you have to
hold open at the rear axle, but I am not sure of your model having this.


"kevind1" > wrote in message
...
>
> Do audi's require a different brake bleeding procedure after you replace
> the master cylinder, I have a 1993 quattro 100cs and I'm having
> problems. Any suggestions?

1984 Audi 4000S Quattro brake bleeding
 

Thanks for the new information. I'll use that trick you said about
bleeding at the master cylinder. I've never tried that before and that
should help. Thanks


--
kevind1
------------------------------------------------------------------------
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View this thread: http://www.audiforum.ca/showthread.php?t=6543