Date: Wed, 24 Mar 2010 20:34:16 -0800
Reply-To: neil n <musomuso@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: neil n <musomuso@GMAIL.COM>
Subject: Re: Proper Brake Pedal Feel/Travel?
In-Reply-To: <068101cacbb2$8daa35c0$6401a8c0@PROSPERITY>
Content-Type: text/plain; charset=ISO-8859-1
On 3/24/10, Scott Daniel - Turbovans <scottdaniel@turbovans.com> wrote:
> what I am going on is ...
> there is a deal where you can press down on a brake pedal, ( on a dual
> master cylinder ) and you feel like it hits something hard inside the MC.
>
> and this is how I think a dual chamber tandem MC works...
> your foot pushes the first piston ....developing pressure,
> now I don't know if the second piston is pushed by a rod or some connection
> between the first piston and the second one ( I doubt it ) or if hydraulic
> pressure from the first piston pushes on the second ( for the rear brakes )
> piston. ...
> but seems like it might be built to work that way.
>
> so...if there is not a good seal within the MC between the two tandem
> chambers ...
> you get that feeling in the pedal..full hydraulic brake force is not being
> achieved to the wheels...
> and the pedal bottoms out on something hard .....I suspect that's the second
> piston you are feeling, which you are not ever supposed to feel.
>
> Looking on page 47.2 of the B. Bible ...
> it shows an exploded view of the MC.
> I notice there's a primary and secondary piston.
> I see a 'stoke limiting screw' ...and also a 'stop sleeve.'
>
I see what you mean. If seal failing/fails, less/no hydraulic force
from primary pushing secondary and primary pins the screw between the
two. Maybe that's what's happening.
> I'm leaning toward your MC so far. for 'leaks internally.'
>
> is your problem more 'can't get a high pedal' or 'can't get good strong
> braking action' ? ...or both ?
Mechanic said he felt no air in system, but pedal feels a little
spongy still. Pedal height actually ok. Braking action seems ok. But
if pedal pushed really hard, at bottom of stroke, it stops on
something. But not like when engine off. i.e. rock hard pedal at
bottom of stroke.
I'm beginning to think the VW mechanic may be wrong.
Maybe I'll install another MC. I'm almost certain my local supplier
has a German one.
A short video I made of pedal. Beginning shows pedal sinking just
after engine started. It's easier to hear pedal bottoming near end of
video.
Youtube:
http://www.youtube.com/watch?v=rC_s2lTJRbE
Neil.
--
Neil Nicholson '81 VanaJetta 2.0 "Jaco"
http://tubaneil.googlepages.com/
http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engines
