Miata Mailing List: January 1999, Message #237

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Todd, here is a more complete version of brake bleeding.  From Miata.net

Pete

L. Brake Fluid

Hydraulic fluid gradually absorbs moisture over time, and this moisture is
potentially damaging to various brake system components.  However, Mazda
recommends only that the brake lines, hoses and connections be "inspected"
at
30,000 mile/30 month intervals; replacement of brake fluid is not mentioned
in
the shop manual for U.S specification cars.   Serious autocrossers, as well
as
those Miata.netters who wish to obtain maximum brake performance, generally
advocate at least yearly brake fluid replacement.  The Miata Club of America
has recommended brake fluid replacement at two year intervals.

The Mazda Shop Manual recommends the following fluid replacement procedure:

1. Remove the brake fluid form the reservoir with a suction pump.

2. Fill the reservoir with clean brake fluid.

3. Attach a vinyl tube to the bleeder screw and place the other end of the
tube in a clear
  container.

4. Pump out the old brake fluid by loosening the bleeder screws one by one,
and
  pumping the brake pedal until only clean fluid is expelled.

5. Fill the reservoir to the specified level.

However, more complete descriptions of brake fluid replacement are found in
the Miata Enthusiast's Manual, as well as in the Miata Club of America
magazine (vol 6(2), p. 52-53, winter 1994):

To replace the brake fluid, the car should be lifted and supported on safety
stands and the wheels removed, as noted above.   Care should be taken to
avoid
spilling any brake fluid onto painted surfaces (it's an excellent solvent),
and to clean any dirt from the master cylinder and from around the bleeder
screws to avoid introducing dirt into the system. The old fluid should be
removed from the reservoir using a suction pump (or turkey baster-like
tool).
Alternatively, one of the bleed screws can be opened (with a bleed tube or
flexible hose over the ball of the bleed screw), and the free end of the
tube
directed into a jar into which sufficient fluid has been added to submerge
the
tube end (to avoid air being reintroduced into the system). The brake pedal
is
then pumped repeatedly until the level falls to the bottom of the reservoir.
An 8 mm brake wrench is required (either the Mazda special service tool, or
a
box-end wrench with a small slot in the box to allow it to slip over the
brake
line).  The bleed screw is typically well-tightened, and the use of an open
Crescent-type wrench may strip the screw.

Fill the reservoir with new fluid (DOT 3 or 4 is recommended).  Starting
from
the caliper furthest from the master cylinder (right rear) and working
around
the car to the nearest (left rear, right front, left front - for left hand
drive cars), bleed each line in turn until fresh fluid emerges from the
bleed
tube.  The reservoir will require re-filling during this process -  usually
after 10 or more pedal strokes.

To avoid any chance for air aspiration into the system, an assistant is
needed
to monitor the bleed valve at the caliper, closing the bleed valve before
one
lifts up on the brake pedal:  Open valve; pump pedal down; close valve; lift
pedal; repeat about 20 times.  Alternatively, a vacuum pump can be used to
draw the fluid out through the bleeder valves.  Such a brake fluid pump is
available through auto supply houses such as Pep Boys, or through some of
the
MCA magazine  advertisers.  Instead of using the brake pedal and master
cylinder to push fluid through the system, the pump uses a hand held vacuum
device that evacuates a small jar.  The jar's lid is vented to a rubber hose
that is placed on the bleeder valve.  When the pump induces a vacuum in the
jar, the vacuum causes brake fluid to flow out of the bleed valve if it is
opened.  Again, it is important to monitor and refill the brake fluid
reservoir periodically during the bleed procedure to avoid introducing air
into the system.  If this occurs, the entire system will require rebleeding.