Date: Thu, 18 May 2006 21:57:42 -0400
Reply-To: Edward Maglott <emaglott@BUNCOMBE.MAIN.NC.US>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Edward Maglott <emaglott@BUNCOMBE.MAIN.NC.US>
Subject: Still can't bleed Brake system
In-Reply-To: <000201c67884$6b12fae0$6400a8c0@masterpc>
Content-Type: text/plain; charset="us-ascii"; format=flowed
I still can't get the front brakes to bleed. Here's the latest I've
tried. I found that if I loosened the brake line from the MC for the rear
brakes and stepped on the pedal, I got a lot of brake fluid out of it. Not
so for the line going to the front brakes. I disconnected the line and
pressed the pedal. I got a little spit of fluid, but it seemed to be
mostly air. I put my finger over the hole for the brake line, and felt
pressure on depressing the pedal, and then suction on releasing the
pedal. Almost like the suction is greater than the pressure...
I broke down and pulled the MC out to bleed it on the bench. I followed
some good instructions I found in the archives about putting plastic tubing
in the outlets and running them back into the reservoir. I think they were
5/16" OD tubing, FYI. They just wedge/screw into the outlets
perfectly. Pumped and pumped and got good flow from both outlets, and
pumped until there was little or no air. Put that whole apparatus back in
the van with the full tubing still in place. Carefully reconnected the
brake lines and tried again, but still nothing or very little at the front
brakes. I left the front bleeders open for 24 hours. The left front
caliper was pretty soaked w/ brake fluid, though not much in the tube on
the bleeder. Fluid seemed to be seeping out the bleeder threads... Rt
front caliper dry.
Tried bleeding again, and thought I was making a little progress, then it
would get to the point of nothing really happening. I had my GF pumping
the pedal. She would push it down and hold, I would open the bleeder, and
the fluid would just barely creep up the tube an inch or so. If I didn't
close the bleeder, it would suck that fluid back in, and then a bunch of
air too. Again, it seems the MC is much more inclined to pull fluid back
in from the brake line than from the reservoir. I did a whole bunch of the
opening and closing with each pump she would do on the pedal, but no
improvement. Tried having her let the pedal back up slowly. Also opened
the rear bleeders so that the pedal would go all the way to the floor, but
that didn't help either.
But wait, there's more! I rigged up a primitive pressure bleeder with air
compressor, piece of inner tube, block of wood. I had to hold it onto the
top of the reservoir, so I couldn't keep it pressurized for very long. But
I did see 20psi on the gauge, and still nothing coming out of the MC outlet
for the front brakes. Could this MC be defective? Its the $50 aftermarket
one from Bus Depot.
Argh! Puzzled Edward
At 09:02 PM 5/15/2006, you wrote:
>The Vanagon brakes are split front/rear, not diagonal. That diagonal
>thing is mostly for light weight front drive cars. The front brakes are
>directly connected to the master cylinder. There is a rear brake
>pressure regulator, mounted on the right side from member near the spare
>tire. There is not an external lever or other bypass means.
>
>The most important part of brake bleeding if you do not have a pressure
>bleeder is patience. Fill the reservoir, open the bleeders and walk away
>for a while. If you are lucky, some fluid will gravity feed through. The
>hard part is getting the chamber in the master filled. Next, close all
>bleeders. See if there is any pedal firmness. If not, open left front,
>depress pedal, close bleeder, release pedal. You should see the fluid
>level in the reservoir drop slightly as the Master sucks it in. Again,
>open bleeder, depress pedal, close bleeder, release pedal. After left
>front has a good flow, go to right front, then go to rears, one at a
>time.
>
>Dennis
>
>-----Original Message-----
>From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
>Of Edward Maglott
>Sent: Monday, May 15, 2006 8:45 PM
>To: vanagon@GERRY.VANAGON.COM
>Subject: Brake system overview
>
>Still trying to bleed my brakes, and getting no, or very little fluid
>from
>the front calipers. See my original message below. Now I'm wondering
>if
>the 2 circuits coming from the master cylinder are really front and
>rear,
>not split diagonally like I thought. Can anybody confirm this? If so,
>which line from the MC is for the front brakes and which for the
>rear? Maybe I need to bleed the offending circuit of the MC better
>before
>trying to bleed the lines.
>
>Edward
>
> >Here's the short version of the events. Replaced Master cylinder.
>Broke
> >off a bleeder on one of the rear cylinders, so the project stalled. I
>went
> >out of town, etc, about 3 weeks pass. Anyway, put in the replacement
>rear
> >wheel cylinder, and start to bleed again. rear wheels bleeding fine.
>At
> >one point I was getting fluid out of LF, but I don't think the RF ever
>was
> >giving me much. Now I pump the pedal and then hold it to the floor,
>open
> >the bleeder and get a very slow minimal flow of fluid. The caliper is
> >actually loose like there is no pressure in it pushing on the piston.
>I
> >suppose it could be seized but I don't think so since it is only a
>year or
> >2 old. And the LF is doing the same thing now.
> >
> >Bentley talks about pushing the lever on the brake pressure regulator
> >toward the rear axe while bleeding. I think that instruction is from
> >another car, since there is no lever on the brake pressure
> >regulator. There is a procedure to test the Brake Pressure regulator,
> >that involves removing it from the body and tilting it forward. Should
>I
> >have to do that to bleed the brakes? I could find no hydraulic
>schematic
> >in the Bentley, but assume this is a dual diagonal braking system.
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