Solution: '83 CGT brake failure

[Scott Fisher <sefisher@cisco.com>]

So on Sunday of this past 3-day weekend, I put the Audi up on jackstands
with the wheels removed, determined to track down what had made the
brake pedal start going all the way to the floor.  Sure enough, there
was a trickle of brake fluid running down the inside of the left rear
wheel.  I removed the brake drum and was horrified at the wet, slimy
black goo inside the drum.  A whole can of brake cleaner later and I was
able to start dismantling things.  As I touched the wheel cylinder,
brake fluid would seep out of the rubber end caps.  No question about
why the reservoir's level was down so far...

I already had brake cylinder rebuild kits (and shoes, for that matter)
courtesy the previous owner (which gives me an idea for how long the
brakes had been weeping), but after installing the seals on the cylinder
there was still a great deal of leakage -- I'd cleaned up the pitting
the best I could but the new seals just wouldn't hold fluid.  I'm never
penny-wise and pound-foolish with brakes, so it was an easy decision to
get new cylinders.

My wife called to find an open parts store so we could finish the job
over the weekend, and she ended up locating two rear wheel cylinders at
a nearby NAPA store (unfortunately Carlsen's parts department was
closed).  I got the first side done Sunday afternoon and did the second
much more quickly the next morning.  Oh, right -- I also reconnected the
handbrake cable that had been left off the hookup on the right-rear
wheel.  Amazing -- now the handbrake goes up only about four clicks and
it'll hold the car solidly, at least on the driveways we've tried out so
far.

In addition to the obvious leaks, there was a good dose of air in the
left front line -- it foamed on the way out of the car.  We bled the old
fashioned way: my wife pressed the pedal, I opened the bleeder, then
closed it when the flow stopped and told her to lift on the pedal.  I've
used gadgets, I've used tricks, I've used a variety of different
techniques and this is the one I rely on when I absolutely positively
want a solid pedal.  Which is to say, any time I work on brakes.  I
recommend it highly -- it's solved problems on a friend's track car
recently too, which had a few bubbles in the rear circuits after he'd
used a Mity-Vac obviously without success.  If the pedal is still spongy
after bleeding it this way, there's a problem somewhere else.

So with the wheels back on the car (swapped front to rear, as well), my
wife hopped in for the test-drive.  Still expecting the
foot-to-the-floor pedal travel, the wheels juddered and chirped in the
driveway as she rolled backwards.  "What did you DO to the brakes?" she
asked.  "The pedal doesn't move at all now!"  She went off for a ride
around the block, then came back with a huge grin and made me get in. 
"You *have* to drive the car now!" she said.  I'm glad she did --
there's now about an inch or less of total pedal travel, at which time
the brakes hook up and the car slows down immediately.  It's neat: hard
pressure doesn't result in more pedal travel, just in more pressure
against the shoulder harness as the car slows down that much faster.  I
like it.

"This is the way brakes are supposed to feel," I said.

"I'll remember that!" she answered.  

Next: repair or replace the driver's seat, the seams are splitting worse
every week.  Then do something about all 27 cracks in the dash, then
perhaps next year we'll do paint.  Kim wants to paint the car Imola
yellow, then do a red-orange candy coat over it for a deep translucent
orange glow...

Tips for working on the rear drums (this'll all make sense once you're
staring at 'em):

  - Make sure you've got a 5mm Allen-head wrench, that's the size you'll
need to remove the wheel cylinders.  Also an 11mm open-end wrench to
disconnect the hard line from where it goes into the cylinder.

  - Loosen the bleed nipple of the wheel cylinder before you try to
place the shoes into position, otherwise it'll be pressurized and you
will force fluid past the seals.

  - The best way I found to reassemble all the shoes, springs, etc was
to hook the handbrake cable to the rear shoe first, then connect all the
springs.  Place the top ends of the brake shoes into the notches in the
wheel cylinder first, and then place the lower end of the rear shoe only
into its notch at the bottom of the back plate.  Then, use vise-grips to
grab the metal part of the forward shoe and lever it into position.

  - If the drum won't go back on, make sure the brake shoes are aligned
evenly front and rear.  Also, you're better off to leave the wheel
bearing out of the drum while you're just slipping it into position,
it's easier to align everything that way.  Then, when you replace the
bearing on the stub axle, it'll centralize everything as you tighten it
down.

  - Slip the box end (closed end) of the 7mm wrench over the bleed
screw, then press the 1/4" clear tubing over the end of it when it comes
time to bleed the system.  Leaving the box-end in place means you can
let go of the wrench if you need to, for example to check the fluid
level in the master cylinder.  

  - Oh, those wretched little anti-rattle spring clips: on the fourth
one I found out The Trick.  There's a pressed steel disc with a slot in
it, meant to slide over the part of the clip that comes through from the
backing plate and goes through the hole in the shoe.  After trying
various unsuccessful techniques, I hit upon this one and it worked in
about three seconds: Use a largeish pair of needle-nose pliers in the
two semicircular cutouts in the perimeter of the disc.  Squeeze the
pliers hard enough that you can press the spring against the shoe, then
when you see the flattened end of the clip protruding through the disc,
rotate the pliers 90 degrees and the clip will snap into the recess
provided for it in the disc.  SO much easier than trying to press them
in by hand and rotate the clip with the pliers...

  - To get the dirty brake fluid out of the bleeding jar and into an
empty Castrol bottle for recycling/disposal: raise the bleeding jar,
place the other end of the bleed hose into the empty bottle, and let
siphon action do the work for you.  

  - While there's a certain discipline and skill involved in
successfully straightening out a cotter pin so it can be reused...  it's
really nice not to have to. :-)

--Scott Fisher
  Sunnyvale, CA