[DeTomaso] Wilwood Brakes WTF????

Sean Korb spkorb at gmail.com
Sun Apr 14 17:29:01 EDT 2013


This may be nonsequitur but I had this problem with my '86 635csi.  THere's
even a recall on the contemporary M model related to this problem.  Over
time (a lot of time, 200,00 miles probably) the aluminum master will build
up a ridge of glaze.  When the system heated up, the piston and ring would
get stuck and the car eventually would cease to move.  Cool it down, and it
would release and you could keep going.  THis happened at all four wheels.
But I was able to ge them to move again after popping the bleeder.  This
may be happening (probably is after what you described) with your calliper
pistons.


On Sun, Apr 14, 2013 at 5:23 PM, Asa Jay Laughton <asajay at asajay.com> wrote:

> I am not an expert, but here are some theories:
>
> You had air in the system, most specifically at the -top- of each
> caliper.  Air compresses, fluid doesn't.  Therefore the bottom pistons
> applied with full force, but the tops didn't; compressing the air
> instead until it reached an equilibrium with the fluid and then pressed
> on the piston.  The difference in all four pistons application against a
> common solid object (the brake pad) caused the pistons to -tilt-
> sideways in the bores.  Note the wedge shape of your pads, tops are
> thick, bottoms are thin, all four pistons are slightly cocked.
>
> With that said, you'd think the pressure against the air at the top
> would distribute to the bottom as well.  Yea, I'd think that too, that's
> why this is just a "theory."  Could it be there is a restriction to the
> top set of pistons that would allow more pressure against the bottom two
> than the top?  Could it be that's a design of the caliper?  Could it be
> the calipers are actually mounted upside down?
>
> What brake fluid are you running?
> When was it last changed?
> When you bled it to take the caliper off, what color was it?
> How dirty did it look?
>
> I think I'd look into the idea that the calipers were mounted upside down?
> Where did you get them?  Dennis Quella?  Send him the pictures and give
> him a call, I bet he'll know the root cause right off the bat.
>
> Asa
>
> Asa Jay Laughton, MSgt, USAFR, Retired
> &  Shelley Marie
> Spokane, WA
> ******************************
> http://www.racingagainstautism.com
> http://www.teampanteraracing.com
> http://facebook.com/racingagainstautism
>
>
> On 4/14/2013 2:07 PM, MikeLDrew at aol.com wrote:
> > Hi guys,
> >
> > So, you may recall my description of me beating the snot out of my
> Pantera
> > at Laguna Seca a couple of weeks ago.   I had a super, super time!
> >
> > Partway through the second session, I started to get some juddering in
> the
> > steering, from the brakes.   I presumed that the cheapo rotors had warped
> > slightly, but I was able to drive through it, and then unwarped when the
> car
> > cooled off.   I noted with some surprise that the front pads had worn
> down
> > 50% in just two 30-minute sessions while the rears looked perfect.   The
> wear
> > was perfectly even.
> >
> > I then had an uneventful three-hour drive home.   During one of my
> stops, I
> > took the time to feel the wheels for any excess heat that might be caused
> > by brake issues, and didn't feel anything untoward.
> >
> > The next time I drove the car, I noted that the brakes were definitely
> > sticking (or at least, SOMETHING was sticking).   I could drive down a
> gentle
> > slope, put it in neutral and the car would gently come to a stop.
> Obviously
> > not right.
> >
> > Today I jacked up the car and pulled the wheels, and was shocked at what
> I
> > found:
> >
> > http://www.poca.com/index.php/gallery/?g2_itemId=39244
> >
> > http://www.poca.com/index.php/gallery/?g2_itemId=39260
> >
> > Both brakes were clearly stuck on, with the pads badly tapered and worn
> > within microns of bare metal on the bottom sides.
> >
> > Since I have 2 psi residual pressure valves in the system, I thought that
> > perhaps the front one had failed and stuck on.   If that was true, then
> it
> > would act almost as if somebody was stepping on the pedal.   To test that
> > theory, I cracked a bleeder on each caliper, expecting brake fluid to
> jet out.
> >
> > Nothing.
> >
> > So the problem is more mechanical in nature, rather than hydraulic.   I
> bit
> > the bullet, pulled the pads and then removed the passenger side caliper.
> > The pistons were very, very difficult to move within the caliper; I
> managed
> > to compress one almost all the way before wising up to the fact that it
> > would be almost impossible to remove if it was flush.   The other three
> came out
> > with some work, that first one came out after a LOT of work.
> >
> > The rubber seals inside the calipers look and feel just fine--having said
> > that, I don't exactly know how they are supposed to feel, but they are
> soft
> > and pliable.   The pistons were covered with brake dust, but a few
> minutes
> > spent with brake cleaner and a rag, and some emory cloth, and everything
> > cleaned up perfectly.
> >
> > http://www.poca.com/index.php/gallery/?g2_itemId=39251
> >
> > So, the question is, what caused this?   Could excessive heat have caused
> > the pistons to expand and swell and jam in the caliper?   Not what I
> would
> > expect from 'racing brakes', and the pedal never went even slightly
> soft, so
> > it's not as if the fluid was boiling.
> >
> > Does anybody have any other theories as to the cause?
> >
> > And more to the point, what should I do now?   I suppose since they are
> 20
> > years old, and apart already, I should probably buy new seals (or new
> seals
> > and pistons?) and swap them out before reassembling everything.   But
> this
> > still begs the question--why did this happen????
> >
> > Looking forward to words of wisdom (along with inspired wild-ass
> guesses!)
> >
> > Mike
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-- 
Sean Korb spkorb at spkorb.org http://www.spkorb.org
'65,'68 Mustangs,'68 Cougar,'78 R100/7,'60 Metro,'59 A35,'71 Pantera #1382
"The more you drive, the less intelligent you get" --Miller
"Computers are useless.  They can only give you answers." -P. Picasso



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