[Shotimes] brakes

[Kevin & Cheryl Airth]

Don:
 Actually this list solved 2 master cylinder failures that I could not
figure out. Both did the same thing after bleeding. The car would stop OK
but not great and the pedal was soft. I was just doing a regular brake
replacement and had a good pedal before the repair. I replaced the M/C both
times and it fixed it but I never could figure out why the M/C went bad. So
after reading this on the list and going to a vacuum pump method, it has not
happened again. So I am not positive that was the problem (I guess I should
have disassembled the old one but had to return the core in rebuildable
condition). It is possible both M/C were leaking by the seals before that.
Both cars were well over 100K miles and 10 years of age. Some of the older
stuff I work on (40+ years or older). I rebuild the M/C myself instead of
just replacing it. These are all filled with much crud and debris. I have
assumed this is because the brake fluid picks up moisture and nobody ever
flushes and changes brake fluid! Also most of them are pitted on the bottom
side of the bore. If not too bad I just hone and install new cups. If it's
still leaks I get them sleeved with stainless steel for a permanent but
expensive repair. It's about $80-$120.

 So in the end my opinion is if the car has had regular brake fluid changes
and flushes. No problem using the brake pedal to bleed. If it's a normal car
and totally unmaintained except when broken. Then use a different method.
.
.



> Kevin,
>
> I can understand what you are talking about, but in about 40
> years of bleeding brakes, I have never had to replace a
> master cyl because of that.  Have you had that problem surface?
>
> Don Mallinson
>
> Kevin & Cheryl Airth wrote:
>
> > Don:
> >  One other point. When using the brake pedal to bleed the brakes,
especially
> > on a high mileage car with the original master cylinder, you are pushing
the
> > pedal farther down than when normally using the brakes. This forces the
> > rubber cups inside the master cylinder thru all the crud that builds up
in
> > the master cylinder over time. This can/might cause you to replace the
M/C
> > shortly after bleeding (It's about $200 too!). Two ways around this.
Don't
> > use the brake pedal to bleed or what I find the easiest. Put a block of
wood
> > under the brake pedal when bleeding so you don't push the pedal all the
way
> > to the floor. Also be sure and flush the brakes at least yearly. I am
now a
> > firm believer in this because of the list!!
> > .
> > .
> >
> >
> >>MY speed bleeder is my son!  With him at the wheels, and me
> >>at the brake pedal (I am the supervisor after all!) it is no
> >>problem bleeding the brakes!  :)
> >>
> >>I also have one of those Vacuum pumps to bleed brakes, but
> >>it is so much trouble to clean up every time, that I rarely
> >>use it if help is available.
> >>
> >>Don Mallinson