-----Original Message-----
From: owner-dakota-truck@bent.twistedbits.net
[mailto:owner-dakota-truck@bent.twistedbits.net] On Behalf Of
jon@dakota-truck.net
Sent: Saturday, September 02, 2006 11:51 AM
To: dakota-truck-moderator@bent.twistedbits.net
Subject: Re: DML: Brake Bleeding
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 --'
Thanks for the detailed info again Jon.
I completed the brake job.
I replaced the 3 front metal lines with premade lines from Advance Auto
since the NAPA Poly Armor lines weren't available. I made some pretty tight
bends by hand with no problems but it doesn't have the special anti
corrosion coating that would have prevented this mess in the first place.
Getting the lines bent just right takes some time. Made sure they weren't
rubbing the frame or body anywhere except where held by the clamps.
For bleeding I used the tube in jar method for the rear and Speed Bleeders
on the front (rear ones weren't in stock). For the passenger rear, I filled
about (3) 3 fl. Oz. jars before the old dark fluid turned clear so it would
seem it takes about 9 fl. oz. to fill the 14 feetish of 3/16" tubing from
the master to the farthest wheel. I wonder what the formula is to figure
out the volume in fluid ounces of a 3/16" line by it's length! Of course we
would need to know the actual ID also. If this were in the subject line, I
know someone here would reply with the answer! I kept going though because
of air bubbles. I assume for the next rear wheel it only had to be bled from
the rear splitter to the wheel because the fluid ran clear a lot faster.
The pass side check valve Speed Bleeder was clogged. I assume from working
on the front lines some crud must have gotten in the lines and clogged the
Speed Bleeder so I bled that side with no bleeder on at all to get any
contaminants out, then used the old bleeder with the Tube In Jar method.
Before doing the driver side caliper, I removed the Speed Bleeder and bled a
few pumps to flush it out, reinstalled the Speed Bleeder and it worked. I
still used a tube and jar to catch the fluid and to watch for bubbles so I
guess the SB really wasn't necessary. I probably wouldn't buy them again.
In my opinion, the tube and jar method works great. I used a clear tube
that was able to squeeze over the small rear bleeder and the larger front
ones. Also, a little Teflon paste (or tape) around the bleeder insures that
the air doesn't come from around the threads of the bleeder when it
loosened.
So I hope the rear lines hold up for a few months. They're rusty also but
not nearly as bad as the front ones were. And like the original poster (I
think Garret) my fuel lines are also covered with rust and pitted in a few
areas.
Thanks for everyone's input.
This archive was generated by hypermail 2b29 : Sun Oct 01 2006 - 01:35:52 EDT