Re: Flushing brake fluid

[Scott Fisher <sefisher@domain.elided>]

Simon Montagu wrote:
> 
> Scott, can you describe the process for a newbie (somewhat mechanically
> "adventurous").

Sure thing (and hoping you don't mind my replying to the Digest; there
may be others out there who could benefit from the info).  I actually
learned a couple of things last weekend that apply to a number of Alfas.

One of the things I learned was that Alfas with dual-circuit braking
systems are bled in a slightly different way from single-circuit cars. 
I'm not sure when the changeover happened at Alfa; in most cars it was
around 1968, so your '71 *probably* has the dual-circuit master
cylinder.  

It's easy to tell: dual-circuit cars have what look like three caps on
the brake fluid reservoir.  The front and rear are actually fluid-level
sensors; the middle one (which is made of metal) is where you fill the
master.  I mention this because single-circuit cars use a slightly
different procedure; it's described in minimal detail in most Alfa
books, but here's what we actually did and learned last weekend.

Brake System Bleeding: Dual-circuit Cars 

Before you begin, you'll need the following:

1 x 7mm open-end wrench
1 x 9mm open-end wrench
1 piece of clear tubing, 1/4" internal diameter (i.d.), approx. 20" long
1 piece of clear tubing, 5/16" i.d., approx. 20" long
Jack and jackstands to support at least one side of the car at a time
1 x 13/16" socket for removing wheels

1.  Place one side of the car on jacks, with both wheels on that side
removed.  Remove the rubber caps on the bleed nipples as well.

2.  Remove the filler cap and mesh strainer from the master cylinder
reservoir.

3.  Place a piece of clear tubing on each bleed nipple, as follows:

  - The 5/16" is a snug fit on the front caliper
  - The 1/4" is a snug fit on the rear caliper

Note that you *can* use 5/16" tubing on front and rear, but the smaller
tubing is less likely to slip off during the process.

4.  Place the free end of each piece of tubing in a small container with
about 1" of fresh brake fluid in the bottom.

5.  Have an assistant press the brake pedal to the floor and hold it.

6.  Open the front bleed screw.  Fluid will pump out; when the fluid
ceases pumping, close the bleed screw.

7.  Open the rear bleed screw.  Fluid will pump out; when the fluid
ceases pumping, close the bleed screw.

8.  Have the assistant release the brake pedal.

9.  As you walk back to the front of the car, check the fluid level in
the master cylinder -- be sure not to let it get low enough that air
gets drawn into the system.  

10.  Repeat the procedure beginning with Step 5.  Look for the
following:

  - bubbles in the fluid coming out of the bleed nipple -- keep flushing
  - discoloration, rust, and other contaminants -- keep flushing
  - clear, clean fluid with no bubbles, rust or gunk -- you're done

11.  Repeat the entire procedure beginning at Step 1 for the other side
of the car.

What Alan Lambert and I found on Saturday was that when I'd open one of
the wheel cylinders, the pedal would drop about halfway to the floor;
when I'd open the other one, it would drop the rest of the way.  This is
what's different about the dual-circuit cars: on a single-circuit
system, the pedal goes all the way to the floor after opening one
cylinder.  The one-corner-at-a-time bleeding procedure would probably
not work properly.

BTW, our results made us both happy.  I got a few bubbles out of the
rear circuit of Alan's car, and the sponginess was much better.  My
brakes still felt softer than the brakes in my Audi, but driving the
Alfa this morning (after driving the Audi all day yesterday) it dawned
on me that the brakes don't feel as hard in the Alfa because I don't
have to PUSH as hard in the Alfa -- it just stops better. :-)

One final comment: the book says that you open both front and rear
cylinders, then slowly pump the pedal till clear fluid comes out.  Alan
and I both felt uncomfortable with that (it seemed too easy to get air
into the system that way), and since we had the two of us there we did
the pump-open-close-release cycle, which prevents any air from entering
the system.  It also means that if a hose slips off the bleed nipple,
there's somebody already right there to pick it up so it doesn't squirt
all over the fender.  I have on occasion used a bleeder hose with a
check valve in the end; two of those would make this a one-person
operation.  And in fact, with the last kit I remember purchasing several
years ago, there were even different sizes of caps to fit over the bleed
nipples.  On the other hand, at 14 cents a foot for 1/4" i.d. tubing and
16 cents for 5/16" tubing, the parts for this are VERY cheap at your
local Orchard Supply Hardware. :-)

Hope this does some good for other Alfisti who didn't know about the
dual-circuit trick!

- --Scott Fisher

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