Brake Question

OK, now i thought i was fairly good with brake issues, but this one has
me stumped.

Always had lots of pedal travel - could always stop but it felt a
little spongey - bled the system twice with no luck. Pedal always feels
resistance and doesnt sink under constant pressure but will go right to
the floor (good sign of air in system, but after two
pressure-bleedings?)
Swapped rotors for some nice new ones, new pads (needed doing, wasnt to
cure this problem) and the problem became more pronounced. Last night i
had to do an emergency stop from 45 and the last car length or so the
pedal just hit the floor and fortunately the car stopped eventually, in
a cloud of smoke (not tyre smoke - didnt slide, the ABS didnt kick in
either). Checked the hoses, fluid levels, new pads and rotors, checked
the hard-lines. Checked the calipers immediately after stopping and
they were just warm to touch, discs were hot naturally.

Any ideas? Should i just re-bleed again and see?

J

On Fri, 21 Oct 2005 04:35:42 -0700, Coyoteboy wrote:
[color=blue]
> OK, now i thought i was fairly good with brake issues, but this one has
> me stumped.
>
> Always had lots of pedal travel - could always stop but it felt a
> little spongey - bled the system twice with no luck. Pedal always feels
> resistance and doesnt sink under constant pressure but will go right to
> the floor (good sign of air in system, but after two
> pressure-bleedings?)
> Swapped rotors for some nice new ones, new pads (needed doing, wasnt to
> cure this problem) and the problem became more pronounced. Last night i
> had to do an emergency stop from 45 and the last car length or so the
> pedal just hit the floor and fortunately the car stopped eventually, in
> a cloud of smoke (not tyre smoke - didnt slide, the ABS didnt kick in
> either). Checked the hoses, fluid levels, new pads and rotors, checked
> the hard-lines. Checked the calipers immediately after stopping and
> they were just warm to touch, discs were hot naturally.
>
> Any ideas? Should i just re-bleed again and see?
>
> J[/color]


You failed to mention the condition of your master cylinder...

"Coyoteboy" <coyoteboyuk@hotmail.com> wrote in message
news:1129894542.328367.99970@g14g2000cwa.googlegroups.com...[color=blue]
> OK, now i thought i was fairly good with brake issues, but this one has
> me stumped.
>
> Always had lots of pedal travel - could always stop but it felt a
> little spongey - bled the system twice with no luck. Pedal always feels
> resistance and doesnt sink under constant pressure but will go right to
> the floor (good sign of air in system, but after two
> pressure-bleedings?)
> Swapped rotors for some nice new ones, new pads (needed doing, wasnt to
> cure this problem) and the problem became more pronounced. Last night i
> had to do an emergency stop from 45 and the last car length or so the
> pedal just hit the floor and fortunately the car stopped eventually, in
> a cloud of smoke (not tyre smoke - didnt slide, the ABS didnt kick in
> either). Checked the hoses, fluid levels, new pads and rotors, checked
> the hard-lines. Checked the calipers immediately after stopping and
> they were just warm to touch, discs were hot naturally.
>
> Any ideas? Should i just re-bleed again and see?
>
> J
>[/color]
What kind of vehicle?

Are the rear brakes drum or disc?

Did you clean the protective coating off of the rotors with brake cleaner
when you replaced them?

What is your history with the vehicle? Have you owned it since new?
Acquired used? Have you check the master cylinder pushrod adjustment?
--
Ray O
correct the return address punctuation to reply

Hachiroku wrote:[color=blue]
>
> You failed to mention the condition of your master cylinder...[/color]

Thats because im not sure on it. The pedal doesnt sink with constant
pressure, and even on excessive travel it always forces back with the
same force i pressed down with hence i assume MC seals are ok. Servo
assembly holds vacuum flawlessly, hose is in perfect condition, as is
the one way valve in it.

J

Ray O wrote:[color=blue]
> "Coyoteboy" <coyoteboyuk@hotmail.com> wrote in message
> What kind of vehicle?
>
> Are the rear brakes drum or disc?
>
> Did you clean the protective coating off of the rotors with brake cleaner
> when you replaced them?
>
> What is your history with the vehicle? Have you owned it since new?
> Acquired used? Have you check the master cylinder pushrod adjustment?
> --
> Ray O
> correct the return address punctuation to reply[/color]

Hehe, so many questions...let me try to answer completely:

Its a '91 Celica Alltrac, vented discs up front, solid rears. Had the
car for 18 months, brakes were initially very good (but anything would
feel that way coming from a Peugeot 205), gradually got worse and i
noticed the pedal travel becoming spongey and increasing. This was when
i first bled it, before the new rotors were fitted. This didnt cure it
but i needed new rotors 6 months later (here we are today) so they have
just been done.

Rotors were cleaned and all mating surfaces were cleaned of junk with
fine sandpaper. This weekend it was bled again, from calipers back to
MC (no change) and back the other way - pushed nearly a litre of fluid
each way. Bled the ABS actuator block by cracking each connecting pipe
- got a couple of squits of air out of it which improved the initial
pedal travel noticably.

Now with the servo vacuum detatched or the engine off the brakes travel
1 inch then firm up nicely and i cant force it past half way with all
my leg strength (you can see the pedal arm flex instead), still feels a
little flexy but not spongey. But with the vacuum *on* I can still hit
the pedal on the floor with a decent bit of force (read as *the force
needed to do an emergency stop*).

I've felt round all the flexi hoses - you can feel them 'stiffen' on
brake application but they certainly dont appear to balloon at all. All
the hard lines were replaced 12 months ago due to excessive corrosion
on one back corner of one line. At the time it didnt make a difference
to the pedal feel so i assume it was bled out fine then (or at least
that hasnt been a contributing factor).

It seems entirely linked to the servo assist unit - with it off it
behaves as normal, with it on it feels like the pedal arm is made of
spring steel. I dont think its the pushrod adjustment - the brakes come
on pretty early - a good bite occuring at about 1 inch, noticable
retardation earlier than that. If only it would stay somewhere near
that one inch mark on firmer application id be happy with them, but it
doesnt and it doesnt seem to exhert any more force on the pads.

J

"Coyoteboy" <coyoteboyuk@hotmail.com> wrote in message
news:1130143680.761882.28020@g43g2000cwa.googlegroups.com...[color=blue]
>
> Ray O wrote:[color=green]
>> "Coyoteboy" <coyoteboyuk@hotmail.com> wrote in message
>> What kind of vehicle?
>>
>> Are the rear brakes drum or disc?
>>
>> Did you clean the protective coating off of the rotors with brake cleaner
>> when you replaced them?
>>
>> What is your history with the vehicle? Have you owned it since new?
>> Acquired used? Have you check the master cylinder pushrod adjustment?
>> --
>> Ray O
>> correct the return address punctuation to reply[/color]
>
> Hehe, so many questions...let me try to answer completely:
>
> Its a '91 Celica Alltrac, vented discs up front, solid rears. Had the
> car for 18 months, brakes were initially very good (but anything would
> feel that way coming from a Peugeot 205), gradually got worse and i
> noticed the pedal travel becoming spongey and increasing. This was when
> i first bled it, before the new rotors were fitted. This didnt cure it
> but i needed new rotors 6 months later (here we are today) so they have
> just been done.
>
> Rotors were cleaned and all mating surfaces were cleaned of junk with
> fine sandpaper. This weekend it was bled again, from calipers back to
> MC (no change) and back the other way - pushed nearly a litre of fluid
> each way. Bled the ABS actuator block by cracking each connecting pipe
> - got a couple of squits of air out of it which improved the initial
> pedal travel noticably.
>
> Now with the servo vacuum detatched or the engine off the brakes travel
> 1 inch then firm up nicely and i cant force it past half way with all
> my leg strength (you can see the pedal arm flex instead), still feels a
> little flexy but not spongey. But with the vacuum *on* I can still hit
> the pedal on the floor with a decent bit of force (read as *the force
> needed to do an emergency stop*).
>
> I've felt round all the flexi hoses - you can feel them 'stiffen' on
> brake application but they certainly dont appear to balloon at all. All
> the hard lines were replaced 12 months ago due to excessive corrosion
> on one back corner of one line. At the time it didnt make a difference
> to the pedal feel so i assume it was bled out fine then (or at least
> that hasnt been a contributing factor).
>
> It seems entirely linked to the servo assist unit - with it off it
> behaves as normal, with it on it feels like the pedal arm is made of
> spring steel. I dont think its the pushrod adjustment - the brakes come
> on pretty early - a good bite occuring at about 1 inch, noticable
> retardation earlier than that. If only it would stay somewhere near
> that one inch mark on firmer application id be happy with them, but it
> doesnt and it doesnt seem to exhert any more force on the pads.
>
> J
>[/color]

I think you're on the correct track - check out the vacuum booster (servo
assist unit).
--
Ray O
correct the return address punctuation to reply

I dont know any clear way of checking it to be honest. The vacuum uni
holds vacuum perfectly well, the one-way valve in the hose works fine -
i cant think of any other test i can run on it :(

A slight alteration to the pedal feel i noticed this morning - if i
press the pedal, while driving, once rapidly i can feel a springy feel
then a sort of 'moving damper' effect - the pedal feels as though its
hit something a little more viscous, then it continues to the floor. If
you press the pedal slowly it takes more travel to hit the 'more
viscous' feeling bit.

I'm almost tempted to go against all my normal feelings and drop it in
at toyota to be checked out, but they'll probably take the pi$$ with
the bill.

J

On Tue, 25 Oct 2005 03:59:01 -0700, Coyoteboy wrote:
[color=blue]
> I dont know any clear way of checking it to be honest. The vacuum uni
> holds vacuum perfectly well, the one-way valve in the hose works fine -
> i cant think of any other test i can run on it :(
>
> A slight alteration to the pedal feel i noticed this morning - if i
> press the pedal, while driving, once rapidly i can feel a springy feel
> then a sort of 'moving damper' effect - the pedal feels as though its
> hit something a little more viscous, then it continues to the floor. If
> you press the pedal slowly it takes more travel to hit the 'more
> viscous' feeling bit.
>
> I'm almost tempted to go against all my normal feelings and drop it in
> at toyota to be checked out, but they'll probably take the pi$$ with
> the bill.
>
> J[/color]

Are you checking the cylider or the booster. This happened to me once a
long time ago, back when I used to PAY someone to fix my cars, and I can't
remember which part they replaced...

I would just go to a junkyard, find a good booster/cyclinder assy and try
it...

Hachiroku wrote:[color=blue]
> Are you checking the cylider or the booster. This happened to me once a
> long time ago, back when I used to PAY someone to fix my cars, and I can't
> remember which part they replaced...[/color]

Well its a hard one to figure out - it only happens when the booster is
active, yet it could still be something in the MC thats failing with
the additional pressure.

[color=blue]
> I would just go to a junkyard, find a good booster/cyclinder assy and try
> it...[/color]

No junkyards round here have anything like the alltrac, and those at
the other end of the country want £100 for a used MC.

J

On Tue, 25 Oct 2005 06:11:25 -0700, Coyoteboy wrote:
[color=blue]
>
> Hachiroku wrote:[color=green]
>> Are you checking the cylider or the booster. This happened to me once a
>> long time ago, back when I used to PAY someone to fix my cars, and I can't
>> remember which part they replaced...[/color]
>
> Well its a hard one to figure out - it only happens when the booster is
> active, yet it could still be something in the MC thats failing with
> the additional pressure.
>
>[color=green]
>> I would just go to a junkyard, find a good booster/cyclinder assy and try
>> it...[/color]
>
> No junkyards round here have anything like the alltrac, and those at
> the other end of the country want £100 for a used MC.
>
> J[/color]

Hmmm...is that part specific to the AllTrac?

Hachiroku wrote:[color=blue]
> Hmmm...is that part specific to the AllTrac?[/color]

Im not sure to be honest. I do know that the alltracs from 87-98 have
about 7 different part numbers with slightly different specifications
for each, depending on whether they are JDM, UK, ABS or not within each
country etc and have heard of problems with fitting even the JDM
version to the same model UK so im guessing they are alltrac specific.
Just my luck eh!

J

On Wed, 26 Oct 2005 02:51:29 -0700, Coyoteboy wrote:
[color=blue]
>
> Hachiroku wrote:[color=green]
>> Hmmm...is that part specific to the AllTrac?[/color]
>
> Im not sure to be honest. I do know that the alltracs from 87-98 have
> about 7 different part numbers with slightly different specifications
> for each, depending on whether they are JDM, UK, ABS or not within each
> country etc and have heard of problems with fitting even the JDM
> version to the same model UK so im guessing they are alltrac specific.
> Just my luck eh!
>
> J[/color]

About right.

My '85 Corolla was the 'new model'. Even thyough the model year started in
September, they were still selling '84s! April of '85 brought the actual
model change, so when I got for parts they ask, "When was it made?" April,
'85. Um...OK...what week! I have to use the VIN (common practice now)
because the car was made in the first week after the change.

And the parts are 2x as expensive!

Hachiroku wrote:[color=blue]
> My '85 Corolla was the 'new model'. Even thyough the model year started in
> September, they were still selling '84s! April of '85 brought the actual
> model change, so when I got for parts they ask, "When was it made?" April,
> '85. Um...OK...what week! I have to use the VIN (common practice now)
> because the car was made in the first week after the change.
>
> And the parts are 2x as expensive![/color]

Funny eh, always the way. Try Peugeots, at least an older one. After
dropping mine into a ditch i replaced the whole rear suspension, front
lower body panels, front lower arms and joints, two alloys and two
driveshafts for £250 - parts from various models of peugeot and
citroen lol.

J