I've been doing some research on this, after David mentioned
the NAPA check valve kit (which are basically the same as the
speed bleeders mentioned by ctandc). I hadn't heard of those
before, and its certainly a good idea.
Anyway, something that I came across during my research which
I wasn't aware of before was that it is easy to rupture seals in
the master cylinder if you use any of the "brake pumping" methods.
Basically the reason for this is normally when you use the brakes,
the pedal only goes down partway. This means that crud and corrosion
can build up on the sides of the piston, the part which is normally
not passing through the seal all the time. Of course, when you are
bleeding the brakes, the pedal can go right to the floor, and when
that happens, the crud built up on the piston is going to pass
through that seal and could easily damage it, depending on the
amount of crud built up. So, if you use the brake pumping method,
just to be on the safe side, be sure to only push the pedal down
as far as it would go during normal braking. Stick something
under the pedal like a piece of 2x4 if you are using an uninformed
helper to pump the brakes. :-)
Another brake bleeding method that I came across is pressure
bleeding. Motive sells a (relatively) inexpensive pressure
bleeder for $50-55. Basically, it looks like a pump style weed
sprayer. You fill it with brake fluid, pump it up to pressurize
it, and a hose runs to what is basically a master cylinder cap
with a hole in the top. Then when you open a bleeder, new fluid
is forced through the master cylinder. This is nice because you
don't have to worry about re-filling the master cylinder all the
time. One catch with the Motive pressure bleeder is that it appears
you need a different master cylinder cap for each type of vehicle that
you work on. (for example, a Ford master cylinder cap may be different
than a GM one). So there might be a little more expense in getting
the caps you need. Or, you might be able to buy a cap and make your
own adapter. Speaking of which, there are a ton of web sites out
there where people have made their own version of this pressure
bleeder. Looks like it would cost about $25 to make. (Google will
turn them up if you are interested in that.) Another catch to this
method is that since it completely fills the master cylinder, you
will need to use something like a syringe or turkey baster to draw
some fluid off the top of the master cylinder prior to putting the
cap back on. Not a big deal, just something to be aware of.
Yet another possibility, and this is something I am considering
picking up to try, is a brake bleeder I stumbled across at Harbor
Freight. (Griots Garage has the same thing for more money.)
Basically this is a combination of the vacuum bleed system and the
pressure bleed system in that it comes with a fitting that sits in
the master cylinder, and there is a bottle full of brake fluid that
you sit upside down on the master cylinder. A tube from the bottle
goes down into the master cylinder, and you turn a valve on.
Basically, this works like those dog or cat waterers, or the office
water cooler. As long as the end of the tube is covered in fluid,
whatever fluid is in the bottle will stay in there, but as soon as
the level drops below the end of the tube, fluid will come out of
the bottle to restore the level of the master cylinder. Once that
is in place, you vacuum bleed the brakes, the kit includes a vacuum
bleeder which you hook up to your air compressor. (There is a venturi
which uses the 90-125psi air compressor air to create a vacuum.) A
large cannister is attached to this unit to collect the brake fluid.
The benefits over the way I normally vacuum bleed the brakes with my
Mighty-vac is the elimination of the need to keep topping off the
master cylinder, and the used brake fluid collection cannister is a
lot bigger than the tiny one on the Mighty-Vac. (You can get larger
cannisters for the Mighty-Vac also.) Of course, it does have the same
limitation of air going past the bleeder threads making it difficult to
tell when the brakes are bled. However, I think what I am going to
do is to try putting some teflon on the bleeder threads to prevent this.
I have seen references to people doing this, and as long as I'm careful
to do it in such a way that it won't get into the brake system, there
shouldn't be any problem with it. Oh, here's a link to that bleeder
I mentioned; best part is its only $20. :-)
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92924
Harbor Freight also has a Mighty-Vac type setup as well as a "tube
in a jar" deal, $20, and $5, respectively. Just do a keyword search on
"bleeder" at harborfreight.com to check 'em out.
So anyway, there's some more brake bleeding info for anyone
who might be interested. :-)
--
-Jon-
.- Jon Steiger -- jon@dakota-truck.net or jon@jonsteiger.com -.
| '96 Kolb Firefly, '96 Suzuki Intruder, Miscellaneous Mopars |
`-------------------------------- http://www.jonsteiger.com --'
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