From: dingbat@codesmth.demon.co.uk (Andy Dingley)
Subject: Re: Brake question
Date: Aug 10, 1995
Message-ID: <808017165.22592@codesmth.demon.co.uk>
Newsgroups: rec.autos.tech

rvl...@pop.com (Robert Vlach) wrote:

>How would I go about changing the brake fluid

Syringe the old stuff out until the reservoir is empty, then fill up
with clean fluid. Bleed the brakes, and carry on doing so until the
fluid emerging from every orifice is clean and fresh. You should
follow the documented bleeding sequence for your vehicle (especially
with diagonal split circuits or ABS). If there isn't a sequence
listed, start from the wheel nearest the master cylinder and work
backwards.

Fluid should be changed every 2-3 years (as a rough guide). Changing
this often discourages the bleedscrews from seizing up, and avoids the
rusting effects of damp fluid. If you've left it longer, or you don't
know how long, or the fluid is black with particles of chewed-up
seals, then you ought to consider doing the seals as well as just
changing the fluid.

You can change to silicone fluid by simply bleeding it through,
although other posters will probably disagree.


--
Andy Dingley                          dingbat@codesmth.demon.co.uk

If all it takes is an infinite number of monkeys with typewriters,
how come AOL haven't written any Shakespeare yet ?

From: dingbat@codesmth.demon.co.uk (Andy Dingley)
Subject: Re: Brake Bleeding
Date: Feb 11, 1996
Message-ID: <311d4e8d.180261258@news.demon.co.uk>
Newsgroups: rec.autos.tech

cain...@postbox.acs.ohio-state.edu (LJC) wrote:

>Today I tried to replace my brake fluid because I've heard it should be
>replaced every few years.

A wise move - few people bother.

> But when I got to the front, as I pumped the pedal, the hose
>connected to the bleeder showed lots of bubbles which kept on coming out.

Were you seeing new bubbles, or the old ones circulating back and
forth ?   I've never had any luck with "auto bleeding valves", so I
still open and close the bleedscrew with a spanner each time the pedal
goes up and down. It's important not to let any fluid flow backwards
into the caliper from the jar.

A better solution is to get a pressure bleeder. These (at their
simplest) are a cheap plastic bottle with two hoses. One has a raneg
of adapters to fit the brake reservoir and the other has a fitting for
your spare tyre. They're _much_ easier to bleed with than using the
pedal, and it really is a one person task. NB - Don't exceed the rated
pressure (usually about 10psi) or you'll spray fluid everywhere.
You'll need to half flatten your tyre and blow it up again afterwards.

You could have air entering the system through some point, but if you
didn't disconnect any pipework and you didn't have a spongy brake
problem beforehand, then I assume the air is coming in backwards,
through the bleedscrew.

From: Andy Dingley <dingbat@codesmiths.com>
Newsgroups: uk.rec.cars.classic
Subject: Re: problem on brake bleeding
Date: Sat, 08 Feb 2003 14:23:27 +0000
Message-ID: <ug4a4v8rdr4a6tmh4ft0e62k11imd0gtg5@4ax.com>

On Sat, 08 Feb 2003 13:07:18 GMT, robwi...@wxs.nl wrote:

>I read
>a couple of times of 'vacuum bleeder devices' announced as
>professional car maintaing equipment...

Then they're simply wrong. There are a couple of designs of master
cylinder where applying a vacuum will suck air in past the seals.

There are also several circuit failure detector valves that will react
badly to vaccum bleeding. Admittedly they're also capable of being
triggered by over-enthusiastic use of pressure bleeders on a single
circuit.


Anyone know how to pressure bleed an Alfasud ?  The level warning
switch fits through a slot in the reservoir filler neck, so you can't
get a seal to a screw-on pressure bleeder.

From: dingbat@codesmiths.com (Andy Dingley)
Subject: Re: Rebuilding caliper - how to press piston back with new s
Date: June 6, 1996
Message-ID: <31c5aab2.13436006@news.demon.co.uk>
Newsgroups: rec.autos.tech

The moving finger of Cliff_...@mindlink.bc.ca (Cliff Lum) having
written:

>Use a Block of wood and Hammer it in.

Can you trust advice from someone who Capitalises words
Inappropriately ?


Why won't the piston push into the caliper ?  Remember we're
rebuilding this caliper, so  we've just cleaned it. There's no dirt or
rust around and we've just had a test assembly without the seal in
place to make sure that the bore isn't scratched, oval or otherwise
unlikely to accept a caliper. The _only_ thing around that can jam the
piston is the rubber seal being slightly proud of its groove. This is
the seal that you're really, really hoping is going to keep your brake
fluid in for the next hundred thousand miles, and you're suggesting
beating hell out of it with a hammer ?   Why stop there ? Why not get
a pick axe ?  Why not drill a hole through the back of the caliper and
use a slide hammer to pull it in ? You'll get the piston into place
and your caliper leaks won't be much worse than if you cut the seal by
pushing the piston through it.

The piston should need more than finger pressure to seat it, but no
more than the palm of your hand. If it needs more than this, something
is _wrong_ so go and fix it, don't just force the bloody thing in
regardless !

Make sure the seal is well lubricated with fresh, clean brake fluid.
Don't use that old grot you took out of the brake bleeding jar (which
people sometimes do). Check also that the piston does _fit_ into the
caliper, for rust & burrs can cause problems that need replacement of
one or the other. Check also that the back of the seal groove is
clean, otherwise the seal won't seat properly. I've never heard of the
compressed air trick (sounds reasonable though), but I have used 3
lengths of 2 thou shim alongside the piston before now on awkward
cases, pulled out as soon as the edge of the piston has seated on the
seal.

--
Andy Dingley                          dingbat@codesmiths.com

If all it takes is an infinite number of monkeys with typewriters,
how come AOL haven't written any Shakespeare yet ?