RE: squeaking and nosediving

[Scott Fisher <sfisher71@domain.elided>]

--- Brian Shorey <bshorey@domain.elided> wrote:
> <snip>
> > Ah.  The Alfa Owner's Manual in front of me (and
> the
> > shop manuals I've owned) clearly say to loosen the
> > bleed screws of the front and rear caliper on the
> same
> > side, pump several times, then end by pressing the
> > pedal down, tightening both bleed screws, and then
> > letting the pedal up.
> <snip>
> 
> Correct me if I'm wrong, but if you loosen the bleed
> screws and then pump
> several times, won't that let air into the system?

Sorry about yesterday's shorthand, I was thinking like
a mechanic and not like a technical writer. :-)

> I was taught to always do the pumping with the bleed
> screws closed,

Okay, okay.  Here's the whole procedure... with one
proviso: I did this only three weeks ago and I'm now
not 100% sure they're 9mm and 7mm wrenches.  They have
been different sizes on all the (stock) Alfas I've
done, including floor-pedal/non-boosted cars and
hanging-pedal/boosted cars... no idea what the brakes
on Mortimer (or the Milano or the GTV6) are like.  

Bleeding 115-series Alfa Dual-circuit Brakes

In the following procedure, "In car" refers to the
person in the car operating the brake pedal and
monitoring the pedal feel.  "Under car" refers to the
person under the car operating the brake bleed screws
and monitoring the condition of the brake fluid for
contamination and bubbles.

Before you begin, you will need the following
equipment and materials:

1 container brake fluid (~16 oz/500ml or more)
2 clear plastic brake bleeding tubes (~1/4" interior
diameter)
2 containers for used brake fluid (16 oz/500ml clear
plastic drinking cups, OR empty brake fluid
containers)
1 9mm box-end wrench
1 7mm box-end wrench
Floor jack 
2 jack stands
An assistant
Rags and/or towels for cleanup

1.  With the engine cover open, raise one side of the
car and remove both wheels.  

2.  Under car: Remove brake bleed screw dust caps (if
present) and master cylinder cap.

3.  Under car: Place wrenches over the flats of each 
bleed screw.  Attach upper end of clear plastic tube
to the bleed screw of the wheel being bled.  Place
lower end of plastic tube in container with
approximately 2" of clean brake fluid (enough that the
end of the tube is below the level of the brake
fluid).  Observe appearance (color, thickness) of
clean brake fluid.

Tip: if you slip the box end (closed end) of the
wrench over the bleed screw before putting the clear
plastic tube over the end of the bleeder, the tube
will hold the wrench in place, making the job slightly
easier.

4.  Under car: check brake fluid level in master
cylinder and refill with clean fluid if below the MIN
mark on side of reservoir.  Say, "Ready to begin."

5.  In car: Press brake pedal to end of travel, then
hold down.  Say, "Open the bleed screws."  Note: as
this procedure is repeated, brake pedal should feel
slightly more firm (and may require less travel) each
time it is pressed.

6.  Under car: Open front bleed screw. Say, "Front
bleed screw is open."  Move to rear of car and open
rear bleed screw.  Say, "Rear bleed screw is open." 
Note condition of brake fluid in clear plastic tubes. 
Look for contamination or bubbles, comparing
appearance against clean brake fluid observed in Step
3.

7.  In car: Keep holding pedal down.  Note: the pedal
will move closer to the floor TWICE with a properly
functioning master cylinder -- once when the person
under car opens each bleed screw.  Say, "Close the
bleed screws."

8.  Under car: Close rear bleed screw.  Say, "Rear is
closed." Close front bleed screw.  Say, "Front is
closed.  Release the pedal."

9.  In car: Release pedal.  Say, "Pedal released."

10.  Under car: Note condition of brake fluid observed
in Step 6.  

If brake fluid contains bubbles or contamination
(looks dirty or black), go to Step 4.

If brake fluid contains no bubbles or contamination
(looks like clean fluid as observed in Step 3),
continue.

11.  Confirm that both bleed screws are tightly
closed.  Remove clear plastic tube from bleed screws,
taking care not to drip brake fluid on paintwork. 
Replace dust caps on bleed screws.  Replace wheels. 
Lower car to floor.

If you have not performed this procedure on both sides
of the car, go to step 1 and repeat for second side.

If you have performed this procedure on both sides of
car, continue.

12.  Check lug nut torque.  Replace master cylinder
cap.  Close engine cover.

END

> Fwiw, I've never heard of a MC causing squeaky
> brakes.  If there is a sudden
> transition between a soft pedal and a hard pedal,
> I'd suspect the booster
> (which may be causing trouble because the MC is
> leaking fluid into it).

Now THAT's a good tip, Brian -- I'm new to
troubleshooting boosted brakes; all the cars I've
redone in the past have been unassisted.  Any
diagnostics for the Alfa brake booster?

--Scott "Close cover before striking" Fisher
  Tualatin, Oregon
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