[Vwdiesel] Weird brakes

[Erik Lane]

Did your problem also start with a new master cylinder replacement? I'm
really hoping not - just for $ reasons for us. :) I'm hoping that somehow it
wasn't installed correctly since that could be a cheap and easy fix...

That's when the problems started for him, so I was thinking either not
installed correctly or bad master cylinder, but I was thinking that the
install was very straightforward and as long as it stopped the car it was
pretty much ok. But since it sounds like there are multiple things that
could be wrong with the install I'm very hopeful that that is all.

But it could be that your tale will come in very handy. If I don't find
anything else then I'll look at the booster. (Well, when I have the master
cylinder off I'll be taking a look at what I can see there, anyway. No point
in not doing a complete job...)

Thank you for telling me your story. Hopefully I won't have to go to quite
the extent you did.

Good job finally finding it!

Erik


On Jan 2, 2008 4:51 PM, Doyt W. Echelberger <doyt at buckeye-express.com>
wrote:

> At 04:09 PM 1/2/2008, you wrote:
> >My brother is having an odd problem on his rabbit, and I don't know what
> to
> >tell him.
>
> ....................Hello Eric......I just ended 4 months of experimenting
> with the same problem on a 1985 Jetta TD that I have owned for about 20
> years. Jettas are a lot like Rabbits.  I'll tell you how I fixed it,
> although the tale is flavored with sad and peppered with frustration. And
> it will be up to you what you say to your brother.
>
>
> >His brakes will work fine for anywhere from 20-50 miles, but then slowly
> >build up pressure until the car wants to stop. If he opens the two
> nozzles
> >on the sides of the master cylinder the pressure releases and is then
> fine
> >again for a while. This happens over and over. He recently put a new
> master
> >cylinder and one new brake line on the car, and afterwards is when this
> >started.
> >My opinion is that the new master cylinder is somehow faulty, but I
> really
> >don't know. This is a strange one that I haven't seen before. Does anyone
> >else out there have any ideas?
> >
> >Thanks!
> >Erik
>  >>>>>>>>>>>>
>
> .......................................I actually replaced the MC twice,
> following the same logic and able to claim they sent a bad one the first
> time.  Problem persisted.
>
> Next, I replaced both front calipers.  Pressure build-up problem remained.
>
> I replaced all the flexible brake hoses. Problem not solved.
>
> All that remained was the vacuum booster....dish shaped unit bolted to the
> firewall.
>
> I Inspected the vacuum booster carefully by feeling every surface with my
> fingertips.....and found extensive rust and corrosion on the back surface
> of the dish. Big flaky crusts of rust. There was some evidence that the
> vacuum booster wasn't holding a vacuum....leak-down test failed when I
> threw a pressure tester  on the system, after disconnecting the hose
> between the booster and the vacuum pump (device mounted where dizzy
> usually
> goes in a gasser.)
>
> I then looked carefully at the cabin-end, where the rod from the brake
> pedal enters the vacuum booster. Noticed that the rod had disturbed the
> features surrounding the booster back door. Rod had been removed during
> both replacements of MC.
>
> To the punch line....I replaced the vacuum booster unit and the pressure
> build-up problem ceased to exist.
>
> This was all very expensive experimentation.  I also think that I
> discovered it is possible to damage both the vacuum booster and the MC
> seals by irreverent manipulation of the actuator rod as it is taken out
> and
> put back in.
>
> And I clearly remember being amazed by the only thing that released the
> build-up during the first few months of experimentation....loosening a
> hard
> line connector on an outlet of the MC and letting the pressure push out
> some brake fluid.
>
> There...you have read my tale of frustration and wallet-thinning
> experimentation, and you need to consider and use the information in
> better
> ways than I did and perhaps tell me if any of it was helpful. And I can't
> guarantee that replacing the vacuum booster will fix your problem, or can
> I
> know if you or someone else has damaged both units by messing with the
> actuator rod.
>
> Peace, fellow traveler,
>
> Doyt
>
>
>
>