HELP: 93 Toyota Corolla vibration problem!

"jim" > wrote in message
...
>> >> I have a 1993ToyotaCorollawith 265k miles on it. There is a
>> >> vibration that has the following symptoms...
>> > <snip>
>>
>> > The solution to the problem was that one of the cups in the master
>> > cylinder was disintegrating. This debris made its way down the line
>> > and clogged the proportioning valve. Thus, when the brake pedal was
>> > released, fluid could not flow unimpeded back to the master cylinder
>> > and brake pressure built up. Replacing both the master cylinder and
>> > the proportioning valve fixed the problem. Thank you to all who
>> > contributed to helping me diagnose this problem.
>>
>> When the master cylinder was suggested there was great howling from some
>> corners.
>
> Seems a bit doubtful there was anything at all wrong with the master
> cylinder.

JESUS CHRIST!!!!!!

See what I mean?

On May 12, 11:32*pm, wrote:
> On Apr 8, 12:21 pm, wrote:> I have a 1993ToyotaCorollawith 265k miles on it. *There is a
> > vibration that has the following symptoms...
>
> <snip>
>
> The solution to the problem was that one of the cups in the master
> cylinder was disintegrating. *This debris made its way down the line
> and clogged the proportioning valve. *Thus, when the brake pedal was
> released, fluid could not flow unimpeded back to the master cylinder
> and brake pressure built up. *Replacing both the master cylinder and
> the proportioning valve fixed the problem. *Thank you to all who
> contributed to helping me diagnose this problem.

Glad to hear the problem is fixed; however, can someone explain to me
how this fix is possible? I have never seen a proportioning valve
that in any way affected the operation of the *front* brakes, is there
something I haven't seen before on the prop valve of the OP's car?

As an aside, if there's rubber debris in any brake component, it's
50/50 whether it came from the master cylinder or not. when I hear of
something like this, my initial reaction is that it's likely rubber
debris from the calipers/wheel cylinders or brake hoses forced
backwards through the system by a technician who did not open the
bleeder screws while pushing the pistons back when replacing the pads/
shoes. However, since as I recall you've already replaced both the
calipers and the hoses, you ought to be good to go.

Also, this whole exercise gives me an excuse to mention that I like to
change the brake fluid in my vehicles every couple years, whether or
not the FSM recommends it. This not only reduces corrosion but
flushes all debris like this "downstream" and out, and most of the
corrosion/rubber failures tend to happen closer to the wheels.

nate

krp wrote:
>
> "jim" > wrote in message
> ...
> >> >> I have a 1993ToyotaCorollawith 265k miles on it. There is a
> >> >> vibration that has the following symptoms...
> >> > <snip>
> >>
> >> > The solution to the problem was that one of the cups in the master
> >> > cylinder was disintegrating. This debris made its way down the line
> >> > and clogged the proportioning valve. Thus, when the brake pedal was
> >> > released, fluid could not flow unimpeded back to the master cylinder
> >> > and brake pressure built up. Replacing both the master cylinder and
> >> > the proportioning valve fixed the problem. Thank you to all who
> >> > contributed to helping me diagnose this problem.
> >>
> >> When the master cylinder was suggested there was great howling from some
> >> corners.
> >
> > Seems a bit doubtful there was anything at all wrong with the master
> > cylinder.
>
> JESUS CHRIST!!!!!!
>
> See what I mean?

Whatever howling you did or you thought some one else did that didn't fix
the problem. Obviously a blockage blockage in the line to the wheel that
had the problem is a reasonable explanation for the symptoms. Replacing
the Master cylinder and proportioning valve may have resulted in a
solution, but there isn't any clear evidence that there was anything wrong
with those parts.

-jim


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On May 13, 9:47 am, N8N > wrote:
> Glad to hear the problem is fixed; however, can someone explain to me
> how this fix is possible? I have never seen a proportioning valve
> that in any way affected the operation of the *front* brakes, is there
> something I haven't seen before on the prop valve of the OP's car?


Nate,
The valve is weird in the 93 corolla. Basically, a line goes from the
master cylinder DIRECTLY to the front driver's side wheel. Then a 2nd
line comes from the master to the valve, which then proportions the
pressure to the passenger side front wheel and BOTH rear wheels (you
read that right... 3 wheels on the valve). Weird eh?

-Jon

On May 14, 12:15*pm, wrote:
> On May 13, 9:47 am, N8N > wrote:
>
> > Glad to hear the problem is fixed; however, can someone explain to me
> > how this fix is possible? *I have never seen a proportioning valve
> > that in any way affected the operation of the *front* brakes, is there
> > something I haven't seen before on the prop valve of the OP's car?
>
> Nate,
> The valve is weird in the 93 corolla. *Basically, a line goes from the
> master cylinder DIRECTLY to the front driver's side wheel. *Then a 2nd
> line comes from the master to the valve, which then proportions the
> pressure to the passenger side front wheel and BOTH rear wheels (you
> read that right... 3 wheels on the valve). *Weird eh?
>
> -Jon

I'd say so! but thanks for the reply, your explanation of the fix
makes more sense now, esp. as I recall you stated that the problem
appeared to be specific to the RF wheel. I wonder what the Toyota
engineers' reasoning for doing this was?

nate