Hi Scott,
Not knowing the entire history of your brake overhaul, I can only make a
few guesses.
First of all, can you actually see any air bubbles coming out? Or are
the brakes simply so far out of adjustment that the pedal goes all the
way to the floor on the first stroke? Typically, if you reassemble
brakes with the shoes way out of adjustment, the pedal will do just what
you have described.
Now, let's assume that you do have some air in the system. There are a
couple of sources to consider.
For example, when you reassemble a master cylinder, there is a lot of
air trapped in it. It's a good idea to "bench bleed" the cylinder before
installing it. If that is inconvenient, you can do it on the vehicle by
attaching a hose from the master cylinder outlet and running it back
into the cylinder reservoir and cycling the fluid until the bubbles
disappear. Then you can connect and bleed the brake lines. If you don't
want to bother with this, you can still eventually get the bubbles out,
but it will just take more pumping.
Another possibility is a leaky cup in the master cylinder that is
allowing air to be drawn in on the backstroke. Honing a master cylinder
too far is a common cause of this condition.
Are you using glycol or silicone fluid? Silicone fluid tends to trap
bubbles more easily than glycol fluid if you pour the fluid into the
reservoir too energetically.
By the way, if you're using glycol fluid, avoid recycling the same fluid
back into the system, since it absorbs more moisture each time it's
exposed to air.
Another way to avoid getting air in the system is to use good "bleeder
screw technique." Have someone press on the pedal, and while the system
is pressurized, open the bleeder screw briefly, then shut it again
BEFORE the pressure dissipates entirely. This will prevent bubbles from
re-entering the wheel cylinder through the hole in the bleeder screw or
through the threads around the screw.
You can also pick up a one-person brake bleeding kit at your local auto
parts store...or make one...for a few bucks. These work pretty well,
except that there is a possibility of air re-entering the system around
the bleeder screw threads. I've seen special bleeder screws that have a
resilient layer around a couple of the threads to seal them, but another
approach is to remove the screw and put a very tiny dab of grease on the
threads. I would not use anti-seize, since it contains aluminum or other
metallic paste that might get into the wheel cylinder.
Hope that gives you some ideas.
Have fun,
Alan
Alan
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