Date: Sun, 21 May 2006 12:31:11 -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: Re: Still can't bleed Brake system
In-Reply-To: <6.0.3.0.0.20060519162918.032a3cd0@buncombe.main.nc.us>
Content-Type: text/plain; charset="us-ascii"; format=flowed
Here's the latest on my brake system. Den mentioned to check the brake
apparatus to be sure there was freeplay when the pedal was released so that
there was not pressure on the piston. I also borrowed a mightvac from a
friend.
I first went to RF wheel and mightyvac pulled 20" Hg. It still got little
fluid and mostly air. I couldn't really tell if air was coming from air
leaking in around the bleeder threads though. Next I went over to LF wheel
and tried. I got a little more fluid, but basically the same
results. Then I took the bleeder all the way out and started getting a
trickle of fluid just by gravity. Checked the bleeder for clogs, it was
fine. I used one of the mightyvac adapters that lets you just plug it
right into the bleeder hole. Then I did get some good fluid, with some
air. The level in the MC reservoir was going down. I probably got 4oz out
of it. Put the bleeder back in, and tried pumping the pedal. Same as
before. Little fluid comes out on the down stroke, and it sucks it all
back in (plus some air) on the upstroke.
Went to the MC and disconnected the line for the front brakes. Put the
clear hose into the output. Same symptom as at the caliper. It pumps
fluid out on the down stroke, but suck at least as much back on the
upstroke. Then connected mightyvac to the outlet on the MC. Pulled 15"
Hg, and got nothing. Tried pumping the pedal, and same as above again,
even with vacuum on the hose. Loosened the MC from the booster to check
for freeplay. I pulled the MC toward me so that there was guaranteed
slack. Pushed on the pedal a little, and then got a whole bunch of fluid
sucked out by the mightvac. I can put the MC all the way up to the
booster, and it doesn't feel like it is starting to push in the piston when
I do this. There is a little play in the pedal, but that doesn't really
mean there is play between the booster and MC piston.
Any diagnoses appreciated. Seems almost like a defective MC to me. Maybe
the cups on the secondary piston installed incorrectly?
Edward
At 04:31 PM 5/19/2006, Edward Maglott wrote:
>Den,
>I did clean out the reservoir when I had it off. That's good advice to
>check the lines. I have heard of very strange behavior with corrosion in
>those flex lines. But, I'm really not getting much flow directly out of
>the MC for the front brake circuit. I think I will try again putting the
>plastic hose in there and bleeding it back into the reservoir.
>
>Edward
>
>At 10:49 AM 5/19/2006, you wrote:
>>Have you ever replaced the flex lines between the caliper and the steel
>>line...
>>
>>To test, open the connection at the flex/steel and press the pedal...
>>
>>WEAR SAFETY GLASSES AS THE FLOW WILL BE SUBSTANTIAL
>>
>>I had the same issue, and new flex lines did the trick...I couldn't even
>>blow through the old ones once I got them off...
>>
>>Additionally....did you flush the reservoir really well before you put it
>>on the new master...I replaced two masters recently on Golf projects
>>because the reservoirs/cylinders had mud in them...seems the fluid goes
>>brown, then black when it breaks down...settles in the bottom of the
>>reservoir where OMG it's right in the path to the master cylinder...talk
>>about planned obsolescence....
>>
>>Good luck...
>>
>>Den.
>>
>>----- Original Message ----- From: "Edward Maglott"
>><emaglott@BUNCOMBE.MAIN.NC.US>
>>To: <vanagon@GERRY.VANAGON.COM>
>>Sent: Thursday, May 18, 2006 9:57 PM
>>Subject: Still can't bleed Brake system
>>
>>
>>>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.
| 
