Re: UrQ brakes?????

[Chris Tucker <tuc@cat.hcp.net>]

Phil,

Ben, Steve and I have narrowed our guesses to either the master cylinder or
hydraulic booster.  Ben has a core hydraulic boost that I'm going to try and if
that doesn't work I'll then replace the master with a S4 master that I know works.

The master that I currently upgraded to is from a 891/2 to 90 200q.  It is the
larger bore master with a 25.4 mm bore.  Same as the 91 200s, S4 and S6s.  As for
as Pentoson, or atf in my case, in the brake fluid, I've pumped so much brake fluid
through the system that everything is spotless.

I'll keep you posted

Chris
tuc@cat.hcp.net
http://www.hcp.net/auid/tucaudi.html

Phil Payne wrote:

> In message <34AF0712.AD0EC703@cat.hcp.net> Chris Tucker writes:
>
> > Not sure if you caught my last note to the list, but I'm still having
> > brake problems.  Unfortunately the bleeding order was
> > not the problem.  So far I've upgrade the master cylinder to a 200Q and
> > have rebuilt the hydraulic booster.
> >
> > I'm still having no brake peddle when my UrQ is running.  The peddle
> > stays firm when the car is off.  When my UrQ is running,
> > the peddle goes smoothly and straight to the floor.  With less, but
> > constant foot pressure, the pressure goes 3/4 down, slows,
> > then goes the rest of the way to the floor.  The peddle feels like it
> > pulsing as if being pushed through the cylinder.
>
> > One more thing, right after I first finished the brakes with the
> > original master, I drove my car around the block.  For a half block the
> > peddle was firm and then starting going to the floor.  I keep hoping
> > it's something simple that I have over looked.  But as time goes I
> > feeling its not something that I have over looked.  Also, I had the same
> > problems with both the original master and the 200 master.  Could the
> > original master have gone bad and I picked up a bad 200 master?
>
> Assuming there are no gross problems (like Pentosin in the brake fluid, or a
> brake fluid leak) then I'm puzzled.  Bad masters is indeed my first thought,
> but it's quite a coincidence.  Have you checked the swept volumes (compared the
> diameters of the masters in the applications) between the original ur-quattro
> and the 200 masters?  There was a diameter change (and hence a volume change)
> at one point.
>
> I'm going to have to throw this one open to the floor - it's beyond my
> competence.
>
> --
>  Phil Payne
>  Committee Member, UK Audi [ur-]quattro Owners Club