My front brakes come on when they want to!

Hi,

I have front disc brakes on my super beetle. I put them on about 2 1/2
years ago. Recently, I found my car pulling to one side. It got
stronger and stronger, slowing my car down; then suddenly it was fine.
about a week later it happened, this time to the other side.After a
mile it would go away.

One day it was pulling VERY hard to the other side, I pulled into the
store I was going to and went in. 10 minutes later when I came out the
brake pedal went to the floor!!!!!!!!!!!! I had no brakes!!!!!!!!!!!!!
?????????????????? No brake fluid on the ground or anywhere. Resevoir
was full.

Being close to home, I thought I could make it using the emergency
brake, and as I kept trying the brakes, they would slowly come up
again, and seemed normal.

A week later ( tonight) they started pulling on one side, then was
fine, then started to pull on the other side. Got home, as I expected
the one front rim was very hot? When I mean pulling, if I let up on the
gas, the brakes would stop my car as if I was doing normal braking (
almost)!!

WHAT IN THE WORLD IS GOING ON HERE????!!!!
Have not changed the brake pads in quite a while, but no matter how
thin they are it should not make a difference.

Would the master cylinder do this? Never had one do this before, but
then again I never had disc brakes with a bad master cylinder. (?)

Are the pistons in the calipers failing? I think they are of good
quality, I got them from aircooled.net

This is bad as it is my daily driver.
Please help!

Thanks!

Matt S

Do you bleed the brakes once or twice a year?
http://www.vw-resource.com/bleed2.html

If that does not help, try a German master cylinder with new brake
light switches.

In article .com>,
wrote:

> Do you bleed the brakes once or twice a year?
> http://www.vw-resource.com/bleed2.html
>
> If that does not help, try a German master cylinder with new brake
> light switches.

It wouldn't be too costly to replace the flex. rubber hose running to
that wheel. they sometimes swell up inside, causing the brake to not
release.
good luck

--
"In the future you may be here, but will your dreams?"

I was thinking about my brake problem as soon as I woke up this
morning.
I want to emphasize, that the brakes would come on without me pushing
on the brake.
I did not think it was the master cylinder as how could the master
cylinder "put on the brakes" strongly without me pushing on the brake
pedal.

What I did this morning was to open up the bleeder bolts ( there are 2
/ caliper).
When I did I noticed there was about a 4 second pause until the fluid
began to flow out.
I thought this is strange.
My thoughts are this? what pulls the caliper piston back in ( away from
the rotor) when the brake pedal is no longer being pushed?
There are no springs..............

It is the fluid being "sucked back in" (so to speak) toward the master
cylinder.
If there is no fluid by the piston, it really is not efficently being
pulled away from the rotor.

So what I think was happening was my brake pads were never sufficently
being pulled away from the rotor ( I noticed my car would not roll as
easily on slight grades in neutral from a dead stop like it used to)
so they were rubbing harder than usual on the rotor.

This gets things real hot, this heat expanded both the air gap and
fluid just enough push on the brakes harder, which made it hotter,
which expanded the air gap and liquid more, which put the brakes on
more...continuing the cycle. ( there were times I was really pushing
the engine hard just to keep the car moving, letting off the gas, the
car would come to a quick stop, pulling on one side). One or the other
front rim was incredibly hot, withthe smell of buring brakes - all
without me ever pushing on the brake pedal!)

After removing the air gap, I noticed my car was rolling very easy in
neutral on slight grades from a standstill.

It gave me no problems today, but I will not feel confidient for about
2 weeks.

If what I did does not work, I'll post back.
If it does work, I'lpost back still

Hope it works!

And thanks for all of your replies, and help.

Matt S.



Crusader george wrote:
> In article .com>,
> wrote:
>
> > Do you bleed the brakes once or twice a year?
> > http://www.vw-resource.com/bleed2.html
> >
> > If that does not help, try a German master cylinder with new brake
> > light switches.
>
> It wouldn't be too costly to replace the flex. rubber hose running to
> that wheel. they sometimes swell up inside, causing the brake to not
> release.
> good luck
>
> --
> "In the future you may be here, but will your dreams?"

The pistons in the caliper are not pulled back when you release the pedal.
They merely float in the last position when the pressure in the line returns
to zero. This enables the pad to remain against the rotor ready for the next
deployment without creating any pressure/friction on the rotor. When you
released the air you effectively reduced the pressure in the line to zero
and allowed the piston to shift position. I would look for warped rotors,
swollen rubber hoses, malfunctioning partition valves or a faulty master
cylinder. Check the endplay on brake pedal at the master as well. If the
master is not allowed to return to the off position it will hold pressure in
the line and cause your problem. As a side note check and repack the wheel
bearing. All that heat will cause the grease to run.


"Matt S" > wrote in message
ps.com...
>I was thinking about my brake problem as soon as I woke up this
> morning.
> I want to emphasize, that the brakes would come on without me pushing
> on the brake.
> I did not think it was the master cylinder as how could the master
> cylinder "put on the brakes" strongly without me pushing on the brake
> pedal.
>
> What I did this morning was to open up the bleeder bolts ( there are 2
> / caliper).
> When I did I noticed there was about a 4 second pause until the fluid
> began to flow out.
> I thought this is strange.
> My thoughts are this? what pulls the caliper piston back in ( away from
> the rotor) when the brake pedal is no longer being pushed?
> There are no springs..............
>
> It is the fluid being "sucked back in" (so to speak) toward the master
> cylinder.
> If there is no fluid by the piston, it really is not efficently being
> pulled away from the rotor.
>
> So what I think was happening was my brake pads were never sufficently
> being pulled away from the rotor ( I noticed my car would not roll as
> easily on slight grades in neutral from a dead stop like it used to)
> so they were rubbing harder than usual on the rotor.
>
> This gets things real hot, this heat expanded both the air gap and
> fluid just enough push on the brakes harder, which made it hotter,
> which expanded the air gap and liquid more, which put the brakes on
> more...continuing the cycle. ( there were times I was really pushing
> the engine hard just to keep the car moving, letting off the gas, the
> car would come to a quick stop, pulling on one side). One or the other
> front rim was incredibly hot, withthe smell of buring brakes - all
> without me ever pushing on the brake pedal!)
>
> After removing the air gap, I noticed my car was rolling very easy in
> neutral on slight grades from a standstill.
>
> It gave me no problems today, but I will not feel confidient for about
> 2 weeks.
>
> If what I did does not work, I'll post back.
> If it does work, I'lpost back still
>
> Hope it works!
>
> And thanks for all of your replies, and help.
>
> Matt S.
>
>
>
> Crusader george wrote:
>> In article .com>,
>> wrote:
>>
>> > Do you bleed the brakes once or twice a year?
>> > http://www.vw-resource.com/bleed2.html
>> >
>> > If that does not help, try a German master cylinder with new brake
>> > light switches.
>>
>> It wouldn't be too costly to replace the flex. rubber hose running to
>> that wheel. they sometimes swell up inside, causing the brake to not
>> release.
>> good luck
>>
>> --
>> "In the future you may be here, but will your dreams?"
>

John Cassara wrote:
> Check the endplay on brake pedal at the master as well. If the
> master is not allowed to return to the off position it will hold pressure in
> the line and cause your problem.

This measurement is very important. There is a check valve in the MC
that allows the fluid back past the piston (in the MC) to the resevoir.
There should be a 1mm gap between the pushrod on the brake pedal, and
the cup inside the rubber boot. This translates into a 5-7mm gap at the
top of the pedal. Lightly press the pedal with your hand and you should
be able to feel when the rod touches the cup. The adjustment is made
via the stop that's bolted to the floor in front of the brake and
clutch pedal. DO NOT ADJUST THE PUSHROD ITSELF. It's common for this
gap to change if the MC is ever changed, or if the carpet ends up being
wedged up in there.
After adjusting the gap, you'll need to readjust the clutch, as the
stop sets the clutch pedal height as well.

Someone else mentioned the rubber flex lines. Even though they might
look perfect on the outside, it is possible they're swollen or
deteriorating on the inside. This will not allow the fluid to come back.

"Matt S" > wrote in message
ps.com...
> My thoughts are this? what pulls the caliper piston back in ( away from
> the rotor) when the brake pedal is no longer being pushed?
> There are no springs..............
>
> It is the fluid being "sucked back in" (so to speak) toward the master
> cylinder.
> If there is no fluid by the piston, it really is not efficently being
> pulled away from the rotor.
>

the fluid is not "sucked" back in...the line pressure is released...the pads
do not get pulled back, only slightly pushed away by the rotor....they
should, and do, remain in slight contact with the rotor....

Please pay a professional. Brakes are very important. Other than lug
nuts, they may just be the most important item on your vehicle. I'd
hate for you to smash into my VW. Who cares about lives, when VW's are
at sake here.

My first question was if you bled the brakes, but several jumped on
that subject allready. I don't have an answer.. sorry.


Matt S wrote:
> Hi,
>
> I have front disc brakes on my super beetle. I put them on about 2 1/2
> years ago. Recently, I found my car pulling to one side. It got
> stronger and stronger, slowing my car down; then suddenly it was fine.
> about a week later it happened, this time to the other side.After a
> mile it would go away.
>
> One day it was pulling VERY hard to the other side, I pulled into the
> store I was going to and went in. 10 minutes later when I came out the
> brake pedal went to the floor!!!!!!!!!!!! I had no brakes!!!!!!!!!!!!!
> ?????????????????? No brake fluid on the ground or anywhere. Resevoir
> was full.
>
> Being close to home, I thought I could make it using the emergency
> brake, and as I kept trying the brakes, they would slowly come up
> again, and seemed normal.
>
> A week later ( tonight) they started pulling on one side, then was
> fine, then started to pull on the other side. Got home, as I expected
> the one front rim was very hot? When I mean pulling, if I let up on the
> gas, the brakes would stop my car as if I was doing normal braking (
> almost)!!
>
> WHAT IN THE WORLD IS GOING ON HERE????!!!!
> Have not changed the brake pads in quite a while, but no matter how
> thin they are it should not make a difference.
>
> Would the master cylinder do this? Never had one do this before, but
> then again I never had disc brakes with a bad master cylinder. (?)
>
> Are the pistons in the calipers failing? I think they are of good
> quality, I got them from aircooled.net
>
> This is bad as it is my daily driver.
> Please help!
>
> Thanks!
>
> Matt S