I did find that unlike the originals, the replacement calipers' bleeder
valves were not at the top of the piston, so there was lots of air in
there. I took them off and hung them with bungees so that the bleeder
should be the highest point of the space inside the caliper. I tried to
let them gravity bleed but after 30-40 minutes still nothing was coming
out and it was getting late. So I pump bled them hanging in that
position. The pedal still only stiffened up to about halfway down.
With the engine running the pedal goes all the way to the floor. But
FWIW the sticking and binding I noticed is not apparent when it's
running. Pedal travel is smooth and very long.

If I weren't borrowing other people's garage and effort I'd set it aside
for another try another day, but I'm out of time for this. There's air
in there but it's somewhere that a gallon and a half of brake fluid pump
bled through the thing apparently can't get to. I drove it home
carefully late at night and the next place it's going is the garage
across the street.

Parking brake works though. That *was* the original goal of the
replacement.

Goes with my profession I guess. Understood in principle -- can't make
it work in real life.

Thanks all, Peter (B.Sc.E. Hons (Eng.Phys.), M.Eng. (Mech.))

Woodchuck wrote:

If you are earning a living as an engineer you must build what you
design. Then you will understand why tradesman curse some engineers
and architects.

Peter Stokes <stokesmanglep (AT) earthlink (DOT) mangle.net> wrote:


Jim B.

Hmmm
So do these calipers have larger pistons? If so that could explain the longer
pedal travel.
Or it could be an issue with the brake booster pushrod and the brake master
too!

just thinking out loud.
later,
dave
Reminder........
Before you criticize someone, you should walk a mile in their shoes. That way,
when you criticize them, you are a mile away from them, and you have their
shoes. Frieda Norris

jimbehning (AT) doesthisblockporkmindspring (DOT) com wrote:
Oh I do know what the tradesmen think of us and why. I wish I could
build more, but engineers are so expensive that professionally you
generally aren't _allowed_ to build anything. You can beg tradesmen for
feedback, but they don't want to look silly either so they often just
"make it work" and don't tell you about it, preferring to curse you
silently. Even as a student, I couldn't get the manufacturing jobs I
wanted, losing out I suppose to brawnier kids who weren't so likely to
get caught thinking too much. Later on, temping between jobs, I was
trying to get an agency to put me in for assembly at a frialator
factory, and they wouldn't do it, not because they suspected I didn't
know about electrical controls and SS finishing, because I did, but
because they thought the ex-cons that ran the floor would beat the crap
out of me. They might be right, but dammit I've tried to build stuff
and people won't let me.

So I'll settle for mostly only getting my hands dirty on my own time and
dime. A very slow apprenticeship... there's so much to learn.

Good day, Peter.

Good that you tried. I have worked with a few folks that I knew would
be happy to stab me in the back just because I wasn't a drunk or
pothead. Be like Roger Brown who is an engineer and does lots of cool
engineering and fabrication in his own personal garage. I get to work
with software engineers who like to get real world feedback. Now not
every product group likes to hear from mere end users but the ones I
have contact with do.

Peter Stokes <stokesmanglep (AT) earthlink (DOT) mangle.net> wrote:


Jim B.

The replacement calipers definitely have larger diameter pistons.
They also, as I mentioned, have the bleeders on the side not the top
of the cylinder as the originals did. The folks I got them from claim
that they're from an 87 GLI (can I confirm or deny this from evidence
on the part?), and that any 85-89 Jetta/Golf/Scirocco rear caliper
will interchange with my 86 GLI. Can anyone confirm or deny that? I
have even been told A5000 2-piston calipers can be retrofitted here
without killing pedal travel like this, although this seems
implausible.

The booster pushrod was pretty loose when I was working on it. The
professional that I handed it over to couldn't fix it by bleeding (I
still need to triple-check that he accounted for the unhelpful
position of the bleeders on the calipers), and when he went to look in
the booster at the pushrod he says it fell out on him. So the
booster's been replaced, and pedal travel is still apparently much too
long. I'm hoping I don't need to change out my mechanic now as well.
I suppose the pushrod could still be wrong -- on the first go-round I
thought of that, but couldn't tell whether it was adjusted by spinning
the whole rod (which appeared to do nothing) or just the acorn nut on
the end (which I couldn't grab to twist) so I left it alone.

Only other suggestion I've had is to check the rear brake pressure reg
for a bleeder.

Thanks, Peter.

Perhaps also the master cylinder on a GLI does not match the one on
the drum brake models. AutoZone (i.e. the remanufacturer who supplies
them) only has one part for disc or drum brake 86 Jettas. My sample
of one VW parts counter says they are different. Maybe I have a m/c
intended only for a GL on there. Anyone know if they're the same?

Good day, Peter.

http://www.autotech.com/brake2.htm
http://www.volksparts.com/A2GLI.htm

The above two places mention a 22mm master cylinder possibly coming standard on
some VWs, but this might be for the 1990-up Jettas.

Maybe you have the 20mm brake master with not enough fluid going to your
calipers. :-( And you need the 22mm since you updated the calipers.

Just thinking out loud!

later,
dave
Reminder........
Before you criticize someone, you should walk a mile in their shoes. That way,
when you criticize them, you are a mile away from them, and you have their
shoes. Frieda Norris

You could try safely clamp down on all of the brake hoses and see what the
brake pedal feels like then. If it is very high and very firm, then you
probably have a problem with the calipers or pads. Then you can release one
clamp at a time to see if that makes a drastic difference.

If it is still going down too far then maybe it is the master or hoses.
I'll still raise an eyebrow with the booster pushrod though!

later,
dave
Reminder........
Before you criticize someone, you should walk a mile in their shoes. That way,
when you criticize them, you are a mile away from them, and you have their
shoes. Frieda Norris

I skimmed thought this post so if this has been covered sorry.

I did a rear disc swap on my rabbit two years ago. I used rear
calipers from an 88 Jetta. I swapped out the proportioning valve for
Scirocco in lines, as well as a newer style 20mm MC and booster.
After a month of bleeding (Pressure bleeders, Gravity, ect.) and
going over everything I could think of someone suggested I flip the
rear calipers over 180deg. I had originally mounted the rear calipers
with the E-brake arm up. So I did as suggested and temporarily
mounted them with the arm down. I installed a rubber line long enough
to allow me to flip the caliper over 180 deg on both rears and
re-bled the system. Only after doing this did I finally get a pedal.
I recently replaced all the calipers, rotors, pads and upgraded to a
22mm MC on this car. I had the same issue until I flipped the rear
calipers to relieve the trapped air. My only suggestion would be if
your rubber line is not long enough to flip the entire caliper, use a
C clamp to hold the piston.
Just my experience.
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