[s-cars] Cold start issue, brake fade

[Vincent Frégeac]

Mark,

As you mentionned your pedal was close to the floor, I suspect the fluid you
used was contaminated with water. I suggest you flush it again, using fresh
Castrol GT LMA or ATE, both high boiling point and reasonnably priced,
flushing the calipers and also the master cylinder, in fact in reverse order
IIRC, MC first then calipers. I personnaly use the Castrol and never had a
problem with it, even when I forgot to reinstall the belly pan after
servicing the car (BTDT a few times).

Beside, with the mushmallow pedal feel of the stock calipers, bad pad fading
can also lead to a pedal going to the floor with almost no braking. In fact,
the pedal would also go to the floor with good pads, it's just that your S4
will be up on its front wheels way before the pedal reach the floor. I
personnaly use Pagid for pads, street savour (good initial grip, no fad,
reasonnable dust), because my usual part suppliers always have them stock,
but there's a lot of other good options.

You can also install Paul's Frankenduct, which is simply a dryer duct vent
installed in the wheel liners so the air coming from the intercooler and oil
cooler flows directly on the brakes, I mean, when the belly pan is installed
and some air is actually flowing through the intercooler and oil cooler.
BTW, for the belly pan, you can contact Force 5 or Shokan. They should have
a few used ones.

Regarding the pedal feel, the braided lines are a pure waste of money with
the stock calipers, IMO. These calipers create a pedal feel which is so bad
you won't notice any difference changing the brake lines. The only advantage
is they will make your wallet lighter, thus slightly increasing the power to
weight ratio of your S4 with driver with wallet (BTDT, but with an S6).

Now, servicing the rear calipers can make a difference. If the hand brake
mechanism in the rear calipers is jammed or partly jammed, it can have an
impact on the pedal feel. When the rear calipers will be nice and shinny,
just get used to pull the handbrake once a day to keep the rear pads close
to the rotors (BTDT on three Audis).

My 0.02$



Vincent.


2006/10/8, Theodore Chen <tedebearp at yahoo.com>:
>
>
> --- Mark Rivera <mrivera at webcats.net> wrote:
> >
> > I flushed and bled the brakes last night, and while it firmed up the
> pedal a
> > little, it's still softer than I'd like.  I'll probably invest in some
> > braided lines soon.  I took the car for a spin after I was done, and
> tried
> > some heavy braking from about 80-45mph.  After about 3-4 applications
> like
> > that, the brakes were fading really bad.  My foot was almost to the
> floor, I
> > was almost out of my seat standing on the pedal, and could not get the
> ABS
> > to activate.  Matter of fact I've never had the ABS step in yet, and I
> > haven't locked a wheel yet either.  I cruised for about 5 minutes to
> cool
> > things down, tried again, and most of the braking had returned.  I know
> the
> > brakes are sorta weak on these cars, but I didn't know it could be this
> bad.
> > I don't wanna pony up for a caliper/rotor upgrade just yet, but would
> like
> > some pad suggestions to replace what I think are stock pads with wear
> > sensors.
>
> mark, what kind of fade?  did the pedal soften and go lower?  or did
> it stay firm, and just feel like higher effort?  the former suggests
> brake fluid fade, the latter suggests pad fade.  you could also have
> both.  did you use fresh brake fluid from a sealed container?
>
> the stock brakes aren't very good, but braking 120-0 on a steep downhill
> worked fine although the effort got noticeably higher (pad fade).
>
> -teddy
>
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