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
>