proportional valve: how important to have working one?

[Pat Korach]

Erik

It sounds like the problem is the proportioning valve.  That
valve compensates for the difference in front and rear braking.
I would assume with the valve in it would have distributed
more pressure to the rear. This is so you would not have the problem
your having.  I experienced this problem about 20 years ago and it
turned out to be that valve.

Just my thought

Pat Korach
Kirkland, WA


Erik Gerrits wrote:

> I am with you in thinking that something may still be
> wrong.  I have bled the brakes numerous times to make
> sure that I have fluid.  Now with the proportioning
> valve removed and a rebuilt MC the rears are slightly
> engaging but the fronts lock up.  It has made today's
> driving really fun, 6 inches of new snow.  Every time
> I used the brakes the fronts were locking up.  The ABS
> will not turn on and that is the only thing left that
> I can think of as to what the problem is with my
> brakes.  The fuse is fine.  If anyone has any idea let
> me know.
>
> Thanks,
> Erik Gerrits
> --- james accordino <ssgacc at yahoo.com> wrote:
> > I think something is definitely wrong.  After I got
> > mine to work again, I played with the setting (that
> > slide nut the spring attaches to) with the ABS off
> > until the rears (usually the right rear) locked up
> > first.  Then I backed it off just a hair.  Now after
> > a
> > real hard run with some serious braking, the rear
> > rotors are smoking hot.  They do stay nice and
> > shiny,
> > and I can definitely say the cars braking is more
> > stabile (much less nose dive or porpoise) and is
> > accomplished in a shorter distance.
> >
> > Jim Accordino
> >
> > --- Erik Gerrits <erik_gerrits at yahoo.com> wrote:
> > > I took mine out completely and I haven't noticed a
> > > difference.  The rears still don't seem to be
> > > working
> > > very much.
> > > Erik Gerrits
> > > 87 5KCSTQ
> > >
> > > --- Bernard Littau <bernardl at acumenassociates.com>
> > > wrote:
> > > > > This is a dealer-only part, I'm told, and is
> > > quite
> > > > expensive even
> > > > > with List
> > > > > discounts.
> > > >
> > > > > >Did anybody feel a difference in praking
> > after
> > > > replacing bad proportional
> > > > > >valve?
> > > > > >
> > > >
> > > > I replaced mine with a used one fresh off a
> > > > front-end wreck 18 months ago.
> > > > I remember it was expensive for a used part.
> > > >
> > > > My original had been left connected when the
> > > > suspension was dropped, so the
> > > > spring was over-stretched and the arm was
> > mangled.
> > > > Near as I could tell it
> > > > was always allowing the minimum brake effect.
> > > >
> > > > The replacement appears to be working correctly,
> > > but
> > > > I have never noticed a
> > > > difference.  I've certainly never locked up the
> > > > rears without the fronts
> > > > locking first with either proportioning valve.
> > > >
> > > > I did buy a fitting that can be used to "bypass"
> > > the
> > > > valve, which would
> > > > present the maximum brake effect to the rears,
> > but
> > > I
> > > > never installed it.
> > > > One of the reasons I didn't try it is because it
> > > > appeared to me the
> > > > proportioning valve never lets 100% brake effect
> > > > through, which the fitting
> > > > would do.  I guess I should try it some time and
> > > > report back.
> > > >
> > > > Best,
> > > >
> > > > Bernard Littau
> > > > Woodinville, WA
> > > > '88 5ktq
> > > >
> > > >
> > >
> > >
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