Date: Sat, 18 Jul 2009 20:26:49 -0700
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Brake problem
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reply-type=response
when you say 'pneumatic sound'
I immediately am wondering if the o-ring on the MC where it bolts to the
booster is in place and OK.
I can't actually think of a time i've replaced a booster on a vanagon
........and I've worked on hundreds of them. I have good used ones, but have
never had an reason to change one out on any vanagon or syncro.
you know the 'booster test' ?
do that test.
also ........I doubt you have this .......but make sure the vaccum line from
engine to booster is fully intact, and 'the full shot' all engine vacuum is
getting
to the booster.
In exteme cases of where there is inheridantly marginal booster power, or
mis-match of brake components .......
it can get tricky.
you couldn't have this since you have a gasoline engine ( I imagine )
....but I read about a case where an extremely expereinced professional
could not get diesel vnaagon brakes to operate strongly, 'no matter what'
..........the eventually-found couse was a very worn engine . There's a
vacuum pump on that engine ....
and the 'non-vacuum' side of the vac. pump on that design, is the crankcase
of the engine ..........very worn engine resulted in lack of proper vaccumm
to the booster.
since it's intermittant .....
it seems that you couldn't possibly have any scenario like that
.........like it does sound like a worn out or faulty brake component.....
all signs point to the booster and mastercylinder area.
if it really is that it's a low pedal most of the time, but once it a while
there is a noise and it works really well.....
all I can think of about that is ..vacuum source, vaccum lines, and booster
.............
and, you can have a master cylinder that seems to bleed fine ....
but there is leakage between the two chambers in the mc ......
when you have that. .......there is just weak and vauge brake action.
I won't use up more bandwidth telling about and SVX syncro , with a rear
brake disc kit ......
that never would get really stelllar brake performance. It worked, and it
stopped, but you couldn't stand on the brake so hard that the nose would
dive, or even try to lock up the tires. I 'did everything' on it, including
checking with a racing brake company about pedal ratio, piston diameters
etc....whoops ! I said I wouldn't ! sorry ! lol. :-)
let us know what you find.
you could swap parts between your two syncro's for testing purposes, but
that's a lot of work.
Scott
www.turbovans.com
----- Original Message -----
From: "Kim Brennan" <kimbrennan@MAC.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Saturday, July 18, 2009 7:35 PM
Subject: Brake problem
> So, last weekend I went through the task of putting in a new brake
> master cylinder on the GoldBrick, my 86 passenger Syncro. It had
> classic symptoms of a failing master cylinder, so that was an obvious
> fix. Flushed the brake fluid, bleed the brakes, and all is happy. Got
> it through Virginia State Safety inspection and its good for another
> year (strange thing is it probably wouldn't make it through a Maryland
> inspection due to some of its rust...but that's a tale for another
> time.)
>
> On my Westy Syncro, however, the brake problem is different. The
> symptoms are as if I had air in the brake lines, but I've bled the
> brakes (and flushed the fluid) all the way around. Essentially if I
> step on the brake pedal and pump it multiple times I'll get braking
> action. However, occasionally, when I hit the brake pedal quickly (and
> release) I'll hear a pneumatic flapping sound (like air going through
> a diaphragm.) When that happens I get excellent brake feel, where
> you'd expect it, about 1 inch after depressing the pedal.
>
> Most of the time, however, its down near the bottom of the floor.
>
> I've been pondering this and considering that it might be the booster,
> but it can't just be that. So I'm going to try and replace the master
> cylinder on this vehicle too. Unless folk have other suggestions as to
> what it might be (discs all around, SA big brakes up front, Smallcard
> (Audi) discs in back...all done within the last 6 years, and I've
> replaced the pads up front, once since the big brakes were installed.)
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