Master Cylinder - WTF?

[patrick.bureau at gmail.com (Patrick Bureau)]

Brian, could it be his new master cylinder wasn't bled right (like you did
mine ?)
 


____
Patrick Bureau, 
85 VW Scirocco, 01 Jeep Cherokee, 05 Honda Reflex Sport
WTB - DFW, Suzuki GS500E/F : http://tinyurl.com/ujc2h 
Reflex Blog : http://reflexscooter.blogspot.com/



-----Original Message-----
From: Brian Wagner [mailto:dagnamit@gmail.com] 
Sent: Thursday, March 29, 2007 2:45 PM
To: Dan Bubb
Cc: scirocco-l@scirocco.org
Subject: Re: Master Cylinder - WTF?

Dan,

The theory of stroking does not apply to new or remanufactured (notice I
didn't say rebuilt). The reason it doesn't hold true on these 2 types is the
complete bore has been stroked to resurface it in preparation for new seals.
So in these 2 types there is no rust accumulation in said bore since they
were flushed and assembled machine oil.

Now if it was rebuilt you have a problem, rebuilds generally only replace
the failed part. So if infact a seal was bad on the plunger they only
replace that, not boring it. Now here is where the problem lies, brake fluid
absorbs moisture right. And we all now that you only stroke 1/2  ~ 3/4 the
length of the bore. So as rust accumulates in the 1/4 that is left, so if
you use the pump/hold/floor method the plunger gets into the rusted area.

And since he is installing new I don't think he has that problem.


On 3/29/07, Dan Bubb <jdbubb@verizon.net> wrote:
>
> Well, just to throw in my >.02.
> I went through the same thing when installing a new MC on my Scirocco. 
> In the end the MC was replaced under warranty and I bought a power 
> bleeder and never had any problem after that.
> The assumption was that even a new MC can be damaged stroking it full 
> stroke like you would if you were bleeding the old fashioned way.
> In your situation the first thing I'd do is run over to Ron's and 
> borrow his power bleeder. ;^) If that doesn't do it then I'd see if 
> the MC can be replaced under warranty.
> Needless to say the power bleeder is a life saver if you have A3 rear 
> calipers that have to be mounted with the bleeder screw on the bottom. 
> It's still a damn good investment for just about any other bleeding
situation.
> Dan
>
> From: "Daun Yeagley" <vwdaun@yahoo.com>
> To: <scirocco-l@scirocco.org>
> Sent: Wednesday, March 28, 2007 11:31 PM
> Subject: Master Cylinder - WTF?
>
>
> > As some of you may know, I just installed a new master cylinder on 
> > Deiter, the '81 S.  It seems as though the old one was leaking fluid 
> > into the brake booster.  And yes, I replaced the brake booster with 
> > an unknown quantity used booster.  (Can't seem to get a new one 
> > now.)
> >
> > First attempt at bleeding the brakes resulted in the semi-expected 
> > snapped bleeder screws in the rear, so I replaced both wheel 
> > cylinders this evening.
> >
> > Filled the brake fluid reservoir and started at the right rear wheel 
> > to work the air out of the system.  I don't have a pressure bleeder, 
> > so I'm stuck with the old "someone pump the pedal while I turn the 
> > bleeder screw" routine.  After working my way around the car, I 
> > still have a brake pedal that shows no real resistance to going to 
> > the floor, AND it seems to have a "catch" in it about 2/3 of the way 
> > down.
> > (Which was present when I started.)
> >
> > So now what?  Have I done something wrong here?
> >
> > Daun Yeagley - Wilmington Ohio
> > '81 Scirocco S (Deiter)       '86 Scirocco 8v
> > '88 Scirocco Slegato (Gino!)  '88 Scirocco 16v
> > '96 Passat GLX Wagon          '56 Cessna 172
> > The first rule of intelligent tinkering is to save all the parts -
> Ehrlich's Law.
> >
> >
> >
> >
> >
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