Boiling brake fluid Redux

So, I got the sliders working very nicely. With the car on the jack
stands, I started it up and nailed the brakes. The wheel is still
sticking, it takes a few rotations for it to free up, but you can still
feel it grabbing. Even after a few rotations, it still grabs. Now, my
firld is computers; brakes are a 'hobby'. When the piston squeezes the
pads, HOW MUCH is it supposed to back off after the release of the pedal?
IS it supposed to back off after the release of the pedal?

I don't have a rebuild kit; I'm going to stop at the local parts store
that is open on Sunday (not the one I get a big discount at :( )and see
what they get for a caliper. Obviously, if it's anywhere NEAR $50, I'll
order one at work.

So the real question is, without having a rebuild kit handy, is there
anything I can do with the materials I have (ie Anti-Seize...) that i can
attempt to get the thing working right? Since it's still up on the jacks
and the wheel isn't tightened yet, it's a 5 minute operation to get in
there and get the caliper off.

I have to go out for an hour, hopefully one of our resident techs can give
me a pointer...

BTW, what I did to free the slider: It came out fairly easily, and didn't
ruin the boot. I ran down to the 'General Store' and got emery cloth,
sanding drums and a 'Dremel' tool (not the real thing) and some
anti-seize.

I yanked the slider, went over it well with the emery cloth and then 1200
grit sandpaper until it was nice and shiny. Then I went out with the
Dremel and a sanding drum and honed out the hole in the caliper until it
was nice and shiny, then hit it with some anti-seize, reistalled the boot,
hit the slider with anti-seize and reassembled. It slides just like it's
supposed to; I thought the problem was solved. Oh, well...

hachiroku <ae86@Trueno.GTS> wrote:
[color=blue]
>So, I got the sliders working very nicely. With the car on the jack
>stands, I started it up and nailed the brakes. The wheel is still
>sticking, it takes a few rotations for it to free up, but you can still
>feel it grabbing. Even after a few rotations, it still grabs. Now, my
>firld is computers; brakes are a 'hobby'. When the piston squeezes the
>pads, HOW MUCH is it supposed to back off after the release of the pedal?
>IS it supposed to back off after the release of the pedal?
>[/color]

Well, I'm no brake expert but I do understand exactly how they
work and I'd venture an opinion that you can't tell anything that
way...they're shoved back just out of solid contact by the
rotating disc and the forces are so high that you can't judge how
much is being applied by a freely spinning wheel...yours sound
fine to me.
[color=blue]
>I don't have a rebuild kit; I'm going to stop at the local parts store
>that is open on Sunday (not the one I get a big discount at :( )and see
>what they get for a caliper. Obviously, if it's anywhere NEAR $50, I'll
>order one at work.
>
>So the real question is, without having a rebuild kit handy, is there
>anything I can do with the materials I have (ie Anti-Seize...) that i can
>attempt to get the thing working right? Since it's still up on the jacks
>and the wheel isn't tightened yet, it's a 5 minute operation to get in
>there and get the caliper off.
>
>I have to go out for an hour, hopefully one of our resident techs can give
>me a pointer...
>
>BTW, what I did to free the slider: It came out fairly easily, and didn't
>ruin the boot. I ran down to the 'General Store' and got emery cloth,
>sanding drums and a 'Dremel' tool (not the real thing) and some
>anti-seize.
>
>I yanked the slider, went over it well with the emery cloth and then 1200
>grit sandpaper until it was nice and shiny. Then I went out with the
>Dremel and a sanding drum and honed out the hole in the caliper until it
>was nice and shiny, then hit it with some anti-seize, reistalled the boot,
>hit the slider with anti-seize and reassembled. It slides just like it's
>supposed to; I thought the problem was solved. Oh, well...[/color]

Sounds like you did it all right...
--


-Gord.

"I'm trying to get as old as I can,
and it must be working 'cause I'm
the oldest now that I've ever been"

On Sun, 24 Jul 2005 18:08:13 +0000, Gord Beaman wrote:
[color=blue]
> hachiroku <ae86@Trueno.GTS> wrote:
>[color=green]
>>So, I got the sliders working very nicely. With the car on the jack
>>stands, I started it up and nailed the brakes. The wheel is still
>>sticking, it takes a few rotations for it to free up, but you can still
>>feel it grabbing. Even after a few rotations, it still grabs. Now, my
>>firld is computers; brakes are a 'hobby'. When the piston squeezes the
>>pads, HOW MUCH is it supposed to back off after the release of the pedal?
>>IS it supposed to back off after the release of the pedal?
>>
>>[/color]
> Well, I'm no brake expert but I do understand exactly how they work and
> I'd venture an opinion that you can't tell anything that way...they're
> shoved back just out of solid contact by the rotating disc and the forces
> are so high that you can't judge how much is being applied by a freely
> spinning wheel...yours sound fine to me.[/color]

Well, I bought some tubing so i can make one of my flushing devices, and
I'm going to at least flush that caliper later.
[color=blue]
>[color=green]
>>I don't have a rebuild kit; I'm going to stop at the local parts store
>>that is open on Sunday (not the one I get a big discount at :( )and see
>>what they get for a caliper. Obviously, if it's anywhere NEAR $50, I'll
>>order one at work.
>>
>>So the real question is, without having a rebuild kit handy, is there
>>anything I can do with the materials I have (ie Anti-Seize...) that i can
>>attempt to get the thing working right? Since it's still up on the jacks
>>and the wheel isn't tightened yet, it's a 5 minute operation to get in
>>there and get the caliper off.
>>
>>I have to go out for an hour, hopefully one of our resident techs can
>>give me a pointer...
>>
>>BTW, what I did to free the slider: It came out fairly easily, and didn't
>>ruin the boot. I ran down to the 'General Store' and got emery cloth,
>>sanding drums and a 'Dremel' tool (not the real thing) and some
>>anti-seize.
>>
>>I yanked the slider, went over it well with the emery cloth and then 1200
>>grit sandpaper until it was nice and shiny. Then I went out with the
>>Dremel and a sanding drum and honed out the hole in the caliper until it
>>was nice and shiny, then hit it with some anti-seize, reistalled the
>>boot, hit the slider with anti-seize and reassembled. It slides just like
>>it's supposed to; I thought the problem was solved. Oh, well...[/color]
>
> Sounds like you did it all right...[/color]

LOL...did I ever mention I used to work for an Aircraft/Aerospace Company?
We made spacesuits, too. No rocket science involved! ;)

On Sun, 24 Jul 2005 17:25:39 GMT, hachiroku <ae86@Trueno.GTS> wrote:
[color=blue]
>So, I got the sliders working very nicely. With the car on the jack
>stands, I started it up and nailed the brakes. The wheel is still
>sticking, it takes a few rotations for it to free up, but you can still
>feel it grabbing. Even after a few rotations, it still grabs. Now, my
>firld is computers; brakes are a 'hobby'. When the piston squeezes the
>pads, HOW MUCH is it supposed to back off after the release of the pedal?
>IS it supposed to back off after the release of the pedal?[/color]

Sounds normal to me. The calipers aren't supposed to back off at
all - there are no return springs in disc brakes like there are on
drum wheel cylinders, but no residual pressure valve either.

The natural thousandth or two of runout in the rotor (along with a
bit of natural slop in the wheel bearings) pushes the pads and
calipers back from the rotor after you release the brake pedal and
start moving. Which is why you hear a little squeaking and groaning
right as you start moving.

With the car up on a jack and the tire being spun by hand, there is
quite a bit of resistance till you move the pads back.

It's also why your system brake fluid volume goes up (and the level
goes down) as the brakes wear - the caliper pistons keep moving
further out.

--<< Bruce >>--

--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
Spamtrapped address: Remove the python and the invalid, and use a net.

Bruce L. Bergman <blPYTHONbergman@earthlink.invalid> wrote in
news:j508e11q4ai470dfhhtfcrg40ks50u0mk3@4ax.com:
[color=blue]
> On Sun, 24 Jul 2005 17:25:39 GMT, hachiroku <ae86@Trueno.GTS> wrote:
>[color=green]
>>So, I got the sliders working very nicely. With the car on the jack
>>stands, I started it up and nailed the brakes. The wheel is still
>>sticking, it takes a few rotations for it to free up, but you can still
>>feel it grabbing. Even after a few rotations, it still grabs. Now, my
>>firld is computers; brakes are a 'hobby'. When the piston squeezes the
>>pads, HOW MUCH is it supposed to back off after the release of the pedal?
>>IS it supposed to back off after the release of the pedal?[/color]
>
> Sounds normal to me. The calipers aren't supposed to back off at
> all[/color]


A normally-operating brake caliper piston will retract a bit (1/32" or so)
when you let off the pedal. This provides the pressure release function.

As gum builds up on the piston, the retraction action is reduced, then
finally stops, resulting in a dragging brake.


--
TeGGeR®

"TeGGeR®" <tegger@tegger.c0m> wrote:
[color=blue]
>Bruce L. Bergman <blPYTHONbergman@earthlink.invalid> wrote in
>news:j508e11q4ai470dfhhtfcrg40ks50u0mk3@4ax.com:
>[color=green]
>> On Sun, 24 Jul 2005 17:25:39 GMT, hachiroku <ae86@Trueno.GTS> wrote:
>>[color=darkred]
>>>So, I got the sliders working very nicely. With the car on the jack
>>>stands, I started it up and nailed the brakes. The wheel is still
>>>sticking, it takes a few rotations for it to free up, but you can still
>>>feel it grabbing. Even after a few rotations, it still grabs. Now, my
>>>firld is computers; brakes are a 'hobby'. When the piston squeezes the
>>>pads, HOW MUCH is it supposed to back off after the release of the pedal?
>>>IS it supposed to back off after the release of the pedal?[/color]
>>
>> Sounds normal to me. The calipers aren't supposed to back off at
>> all[/color]
>
>
>A normally-operating brake caliper piston will retract a bit (1/32" or so)
>when you let off the pedal. This provides the pressure release function.
>
>As gum builds up on the piston, the retraction action is reduced, then
>finally stops, resulting in a dragging brake.[/color]

We're likely arguing nits here but I don't see why the piston
would 'retract' at all...it will be 'shoved back' into it's
'hole' slightly by any slight wobble or unevenness in the turning
disc but as long as the caliper is free to move sideways and the
piston is free to move in and out then the disc will shove the
piston out of it's way (so to speak). I don't see any action in
the system that would cause the piston to 'retract' (I equate
'retract' as the piston being 'pulled' back inside it's cylinder
and not being 'pushed' into it)
--


-Gord.

"I'm trying to get as old as I can,
and it must be working 'cause I'm
the oldest now that I've ever been"

Gord Beaman <gord@islandtelecom.com> wrote in
news:8f68e1tb3mc0na2ol176cq5d3liltasloo@4ax.com:
[color=blue]
> "TeGGeR®" <tegger@tegger.c0m> wrote:[/color]
[color=blue][color=green]
>>A normally-operating brake caliper piston will retract a bit (1/32" or
>>so) when you let off the pedal. This provides the pressure release
>>function.
>>
>>As gum builds up on the piston, the retraction action is reduced, then
>>finally stops, resulting in a dragging brake.[/color]
>
> We're likely arguing nits here but I don't see why the piston
> would 'retract' at all[/color]



It does. Go pull your caliper and look for yourself.


--
TeGGeR®

"TeGGeR®" <tegger@tegger.c0m> wrote:
[color=blue]
>Gord Beaman <gord@islandtelecom.com> wrote in
>news:8f68e1tb3mc0na2ol176cq5d3liltasloo@4ax.com:
>[color=green]
>> "TeGGeR®" <tegger@tegger.c0m> wrote:[/color]
>[color=green][color=darkred]
>>>A normally-operating brake caliper piston will retract a bit (1/32" or
>>>so) when you let off the pedal. This provides the pressure release
>>>function.
>>>
>>>As gum builds up on the piston, the retraction action is reduced, then
>>>finally stops, resulting in a dragging brake.[/color]
>>
>> We're likely arguing nits here but I don't see why the piston
>> would 'retract' at all[/color]
>
>
>
>It does. Go pull your caliper and look for yourself.[/color]

Can you explain why?
--


-Gord.

"I'm trying to get as old as I can,
and it must be working 'cause I'm
the oldest now that I've ever been"

Gord Beaman <gord@islandtelecom.com> wrote in
news:jed8e1prche011muhvrea706tkuaicrupl@4ax.com:
[color=blue]
> "TeGGeR®" <tegger@tegger.c0m> wrote:
>[/color]
[color=blue][color=green][color=darkred]
>>> We're likely arguing nits here but I don't see why the piston
>>> would 'retract' at all[/color]
>>
>>
>>
>>It does. Go pull your caliper and look for yourself.[/color]
>
> Can you explain why?[/color]


Don't know for sure. My guess is the return springs inside the master
cylinder are responsible. In pushing the seals back, they suck the fluid
back as well, and if the piston is free to move, it gets sucked in too.

But they *do* pull back in a bit after you let of of the pedal. I see that
all the time. It's one way I have of telling what sort of shape the piston
is in. If there's no pull-back, there's buildup of some kind on the piston.

--
TeGGeR®

The Unofficial Honda/Acura FAQ
[url]www.tegger.com/hondafaq/[/url]

"TeGGeR®" <tegger@tegger.c0m> wrote:
[color=blue]
>Gord Beaman <gord@islandtelecom.com> wrote in
>news:jed8e1prche011muhvrea706tkuaicrupl@4ax.com:
>[color=green]
>> "TeGGeR®" <tegger@tegger.c0m> wrote:
>>[/color]
>[color=green][color=darkred]
>>>> We're likely arguing nits here but I don't see why the piston
>>>> would 'retract' at all
>>>
>>>
>>>
>>>It does. Go pull your caliper and look for yourself.[/color]
>>
>> Can you explain why?[/color]
>
>
>Don't know for sure. My guess is the return springs inside the master
>cylinder are responsible. In pushing the seals back, they suck the fluid
>back as well, and if the piston is free to move, it gets sucked in too.
>
>But they *do* pull back in a bit after you let of of the pedal. I see that
>all the time. It's one way I have of telling what sort of shape the piston
>is in. If there's no pull-back, there's buildup of some kind on the piston.[/color]

Ok, makes sense...thanks Teg.
--


-Gord.

"I'm trying to get as old as I can,
and it must be working 'cause I'm
the oldest now that I've ever been"

On Sun, 24 Jul 2005 23:03:52 +0000, Gord Beaman wrote:
[color=blue]
> "TeGGeR®" <tegger@tegger.c0m> wrote:
>[color=green]
>>Bruce L. Bergman <blPYTHONbergman@earthlink.invalid> wrote in
>>news:j508e11q4ai470dfhhtfcrg40ks50u0mk3@4ax.com:
>>[color=darkred]
>>> On Sun, 24 Jul 2005 17:25:39 GMT, hachiroku <ae86@Trueno.GTS> wrote:
>>>
>>>>So, I got the sliders working very nicely. With the car on the jack
>>>>stands, I started it up and nailed the brakes. The wheel is still
>>>>sticking, it takes a few rotations for it to free up, but you can still
>>>>feel it grabbing. Even after a few rotations, it still grabs. Now, my
>>>>firld is computers; brakes are a 'hobby'. When the piston squeezes the
>>>>pads, HOW MUCH is it supposed to back off after the release of the
>>>>pedal? IS it supposed to back off after the release of the pedal?
>>>
>>> Sounds normal to me. The calipers aren't supposed to back off at
>>> all[/color]
>>
>>
>>A normally-operating brake caliper piston will retract a bit (1/32" or
>>so) when you let off the pedal. This provides the pressure release
>>function.
>>
>>As gum builds up on the piston, the retraction action is reduced, then
>>finally stops, resulting in a dragging brake.[/color]
>
> We're likely arguing nits here but I don't see why the piston
> would 'retract' at all...it will be 'shoved back' into it's 'hole'
> slightly by any slight wobble or unevenness in the turning disc but as
> long as the caliper is free to move sideways and the piston is free to
> move in and out then the disc will shove the piston out of it's way (so to
> speak). I don't see any action in the system that would cause the piston
> to 'retract' (I equate 'retract' as the piston being 'pulled' back inside
> it's cylinder and not being 'pushed' into it)[/color]

Before I read Teg's response, I'm going to take a guess: there will be
some retraction (not much) when you take your foot off the brake pedal.
Think of fluid dynamics: you've pressed the pedal, and introduced pressure
into the system. Take your foot off the brake, and the release of pressure
will cause a small amount of back pressure, sucking the caliper back in
just slightly.

Just an educated guess...

Did you take out the two pins, clean them and then lub them with a good
synthetic break lube?

Richard.

hachiroku <ae86@Trueno.GTS> wrote:
[color=blue]
>On Sun, 24 Jul 2005 23:03:52 +0000, Gord Beaman wrote:
>[color=green]
>> "TeGGeR®" <tegger@tegger.c0m> wrote:
>>[color=darkred]
>>>Bruce L. Bergman <blPYTHONbergman@earthlink.invalid> wrote in
>>>news:j508e11q4ai470dfhhtfcrg40ks50u0mk3@4ax.com:
>>>
>>>> On Sun, 24 Jul 2005 17:25:39 GMT, hachiroku <ae86@Trueno.GTS> wrote:
>>>>
>>>>>So, I got the sliders working very nicely. With the car on the jack
>>>>>stands, I started it up and nailed the brakes. The wheel is still
>>>>>sticking, it takes a few rotations for it to free up, but you can still
>>>>>feel it grabbing. Even after a few rotations, it still grabs. Now, my
>>>>>firld is computers; brakes are a 'hobby'. When the piston squeezes the
>>>>>pads, HOW MUCH is it supposed to back off after the release of the
>>>>>pedal? IS it supposed to back off after the release of the pedal?
>>>>
>>>> Sounds normal to me. The calipers aren't supposed to back off at
>>>> all
>>>
>>>
>>>A normally-operating brake caliper piston will retract a bit (1/32" or
>>>so) when you let off the pedal. This provides the pressure release
>>>function.
>>>
>>>As gum builds up on the piston, the retraction action is reduced, then
>>>finally stops, resulting in a dragging brake.[/color]
>>
>> We're likely arguing nits here but I don't see why the piston
>> would 'retract' at all...it will be 'shoved back' into it's 'hole'
>> slightly by any slight wobble or unevenness in the turning disc but as
>> long as the caliper is free to move sideways and the piston is free to
>> move in and out then the disc will shove the piston out of it's way (so to
>> speak). I don't see any action in the system that would cause the piston
>> to 'retract' (I equate 'retract' as the piston being 'pulled' back inside
>> it's cylinder and not being 'pushed' into it)[/color]
>
>Before I read Teg's response, I'm going to take a guess: there will be
>some retraction (not much) when you take your foot off the brake pedal.
>Think of fluid dynamics: you've pressed the pedal, and introduced pressure
>into the system. Take your foot off the brake, and the release of pressure
>will cause a small amount of back pressure, sucking the caliper back in
>just slightly.
>
>Just an educated guess...[/color]

Pretty close Hach...as teg says, the master cyl piston is shoved
back by a spring...now the seal on that piston has to 'unseal' so
as to be 'ready' to 'grab' more fluid if it's necessary so there
has to be a very slight negative pressure on the fluid in the
system as it unseal and this is what moves the slave pistons
slightly. Remember that there's four slave cylinders and they're
all much bigger than the master cyl therefore they'll all move
only a slight amount...that sound about right Teg?
--


-Gord.

"I'm trying to get as old as I can,
and it must be working 'cause I'm
the oldest now that I've ever been"

Gord Beaman <gord@islandtelecom.com> wrote in
news:a6u9e1pjt92v1qmb8tmf110nloqt39ii83@4ax.com:

[color=blue]
> Pretty close Hach...as teg says, the master cyl piston is shoved
> back by a spring...now the seal on that piston has to 'unseal' so
> as to be 'ready' to 'grab' more fluid if it's necessary so there
> has to be a very slight negative pressure on the fluid in the
> system[/color]


There would only be negative pressure so long as the return ports are still
closed One the seals pass the return port, pressure is equalized. And if
the fluid warms up appreciably while it's compressed (such as when the
brakes get hot), there will be POSITIVE pressure until the return ports
open. That's how a misadjusted M/C pushrod causes the brakes to lock on as
you drive.

I made up this page:
[url]http://www.tegger.com/hondafaq/mastercylinderreplace/howworks.html[/url]
It's for a Honda, but the idea is the same.

[color=blue]
> as it unseal and this is what moves the slave pistons
> slightly. Remember that there's four slave cylinders and they're
> all much bigger than the master cyl therefore they'll all move
> only a slight amount...that sound about right Teg?[/color]


Could be. I'm not up on the physics of it. All I know is what I see.



--
TeGGeR®

The Unofficial Honda/Acura FAQ
[url]www.tegger.com/hondafaq/[/url]

On Mon, 25 Jul 2005 11:17:35 +0000, Richard wrote:
[color=blue]
> Did you take out the two pins, clean them and then lub them with a good
> synthetic break lube?
>
> Richard.[/color]

See my subsequent posts...I...I've tried everything. Just giving up and
ordering a new caliper and hose...