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Next: Dumbstruck
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External
Since: Mar 07, 2004
Posts: 24
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(Msg. 1) Posted: Sun Dec 12, 2004 10:40 pm
Post subject: Soft/Spongy Brakes
Archived from groups: alt>autos>bmw (more info?)
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Hello All,
I replaced front pads and rotors today on the 1993 740i (116K). Job went
very smoothly. The pads were down to about only 10% meat left.
The brake pedal has been very spongy lately and the pedal travel is almost
to the floor before you get any bite.
I thought that once I replaced these well-worn pads, the pedal would come
up, but it didn't.
Here is my plan:
Step 1: Check the rear rotors and pads, though I looked about 6 months ago
and they had about 60% wear. If they still have some meat, I will proceed
directly to step 2.
Step 2: Bleed the entire brake system.
I hope that one of these get it for me. My google searches have mentioned
bad master cylinders as culprits for soft brakes--any thoughts?
I figured I would post and see if anyone else has had any experiences like
mine. Cross your fingers that bleeding these lines will do the trick.
ER |
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External
Since: Sep 12, 2003
Posts: 363
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(Msg. 2) Posted: Mon Dec 13, 2004 12:19 am
Post subject: Re: Soft/Spongy Brakes [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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"EggRaid" <shaderushmore DeleteThis @yahoo.com> wrote in message
news:Lp7vd.28868$Eq.27588@fe1.texas.rr.com...
> Hello All,
>
> I replaced front pads and rotors today on the 1993 740i (116K). Job went
> very smoothly. The pads were down to about only 10% meat left.
>
> The brake pedal has been very spongy lately and the pedal travel is almost
> to the floor before you get any bite.
>
> I thought that once I replaced these well-worn pads, the pedal would come
> up, but it didn't.
>
> Here is my plan:
>
> Step 1: Check the rear rotors and pads, though I looked about 6 months ago
> and they had about 60% wear. If they still have some meat, I will proceed
> directly to step 2.
>
> Step 2: Bleed the entire brake system.
>
> I hope that one of these get it for me. My google searches have mentioned
> bad master cylinders as culprits for soft brakes--any thoughts?
>
> I figured I would post and see if anyone else has had any experiences like
> mine. Cross your fingers that bleeding these lines will do the trick.
>
> ER
Sure sounds like you need a bleed, I'd go for that first, after replacing
the fluid. If you track your car you're not allowed fluid older than 6
months by BMWCCA driving school rules. I'd go no longer than 2 years on the
street. Once it gets contaminated all the bleeding and new pads in the
world won't cure it.
-Russ.<!-- ~MESSAGE_AFTER~ --> |
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External
Since: Jun 22, 2004
Posts: 1299
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(Msg. 3) Posted: Mon Dec 13, 2004 7:40 am
Post subject: Re: Soft/Spongy Brakes [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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In article <Lp7vd.28868$Eq.27588@fe1.texas.rr.com>,
EggRaid <shaderushmore.TakeThisOut@yahoo.com> wrote:
> I replaced front pads and rotors today on the 1993 740i (116K). Job
> went very smoothly. The pads were down to about only 10% meat left.
> The brake pedal has been very spongy lately and the pedal travel is
> almost to the floor before you get any bite.
> I thought that once I replaced these well-worn pads, the pedal would
> come up, but it didn't.
Usual reason is air in the system. If you're unsure of the age, change the
fluid. It should be done every two years anyway. However, air in the
system usually indicates a fault elsewhere as it has to come from
somewhere. And as you say the likely cause is the master cylinder.
--
*Can fat people go skinny-dipping?
Dave Plowman dave.TakeThisOut@davenoise.co.uk London SW
To e-mail, change noise into sound.<!-- ~MESSAGE_AFTER~ --> >> Stay informed about: Soft/Spongy Brakes |
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External
Since: Dec 07, 2004
Posts: 126
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(Msg. 4) Posted: Mon Dec 13, 2004 9:19 am
Post subject: Re: Soft/Spongy Brakes [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Not necessarily. It's recommended that brake fluid is changed every
two years simply 'cos it degrades (by design). A faulty master
cylinder won't necessarily introduce air - it just won't maintain
pressure. >> Stay informed about: Soft/Spongy Brakes |
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External
Since: Jun 22, 2004
Posts: 1299
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(Msg. 5) Posted: Mon Dec 13, 2004 2:40 pm
Post subject: Re: Soft/Spongy Brakes [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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In article <1102954760.037167.207950.TakeThisOut@z14g2000cwz.googlegroups.com>,
<adder1969.TakeThisOut@yahoo.co.uk> wrote:
> It's recommended that brake fluid is changed every
> two years simply 'cos it degrades (by design).
It absorbs moisture. Not through design, though.
> A faulty master cylinder won't necessarily introduce air - it just
> won't maintain pressure.
Not necessarily. But if there are no signs of leaks, and bleeding doesn't
cure things it would be my first guess. YMMV.
Could be the last fluid change wasn't properly carried out and some air
remains. Who knows?
--
*When blondes have more fun, do they know it?
Dave Plowman dave.TakeThisOut@davenoise.co.uk London SW
To e-mail, change noise into sound.<!-- ~MESSAGE_AFTER~ --> >> Stay informed about: Soft/Spongy Brakes |
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External
Since: Feb 01, 2004
Posts: 27
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(Msg. 6) Posted: Mon Dec 13, 2004 8:40 pm
Post subject: Re: Soft/Spongy Brakes [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Master cylinders can pull air from atmosphere on the release of the
pedal. The fluid absorbs moisture from the air which impairs it's
hydraulic capabilities, so could be either really. Best do the fluid
first and if it is OK after that for a while and then goes soft again it
will probably be the cylinder.
Good luck!
Clive >> Stay informed about: Soft/Spongy Brakes |
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External
Since: Dec 07, 2004
Posts: 126
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(Msg. 7) Posted: Tue Dec 14, 2004 7:40 am
Post subject: Re: Soft/Spongy Brakes [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Moisture is absorbed by the fluid *by design* to avoid the water
vapourising when the brakes get hot and then and only then impairing
the hydraulic properties. You could use water in your brake lines if
they never got hot & you weren't worried about corrosion.
Vapourisation of old fluid and/or corrosion can lead to gases in the
fluid (which leads to corrosion etc etc) >> Stay informed about: Soft/Spongy Brakes |
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External
Since: Dec 07, 2004
Posts: 126
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(Msg. 8) Posted: Tue Dec 14, 2004 8:04 am
Post subject: Re: Soft/Spongy Brakes [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Moisture is absorbed by the fluid *by design* to avoid the water
vapourising when the brakes get hot and then and only then impairing
the hydraulic properties. You could use water in your brake lines if
they never got hot & you weren't worried about corrosion.
Vapourisation of old fluid and/or corrosion can lead to gases in the
fluid (which leads to corrosion etc etc) >> Stay informed about: Soft/Spongy Brakes |
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External
Since: Jun 22, 2004
Posts: 1299
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(Msg. 9) Posted: Tue Dec 14, 2004 11:40 am
Post subject: Re: Soft/Spongy Brakes [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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In article <1103035222.411454.226630.TakeThisOut@z14g2000cwz.googlegroups.com>,
<adder1969.TakeThisOut@yahoo.co.uk> wrote:
> Moisture is absorbed by the fluid *by design* to avoid the water
> vapourising when the brakes get hot and then and only then impairing
> the hydraulic properties.
Then silicone brake fluid could never work, as it doesn't absorb moisture.
--
*Heart attacks... God's revenge for eating his animal friends
Dave Plowman dave.TakeThisOut@davenoise.co.uk London SW
To e-mail, change noise into sound.<!-- ~MESSAGE_AFTER~ --> >> Stay informed about: Soft/Spongy Brakes |
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External
Since: Feb 01, 2004
Posts: 27
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(Msg. 10) Posted: Tue Dec 14, 2004 10:40 pm
Post subject: Re: Soft/Spongy Brakes [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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External
Since: Dec 07, 2004
Posts: 126
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(Msg. 11) Posted: Wed Dec 15, 2004 4:04 am
Post subject: Re: Soft/Spongy Brakes [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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External
Since: Nov 08, 2004
Posts: 528
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(Msg. 12) Posted: Wed Dec 15, 2004 10:28 am
Post subject: Re: Soft/Spongy Brakes [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Soft, spongy brake pedal is usually a sign of air in the system.
"EggRaid" <shaderushmore.TakeThisOut@yahoo.com> wrote in message
news:Lp7vd.28868$Eq.27588@fe1.texas.rr.com...
> Hello All,
>
> I replaced front pads and rotors today on the 1993 740i (116K). Job went
> very smoothly. The pads were down to about only 10% meat left.
>
> The brake pedal has been very spongy lately and the pedal travel is almost
> to the floor before you get any bite.
>
> I thought that once I replaced these well-worn pads, the pedal would come
> up, but it didn't.
>
> Here is my plan:
>
> Step 1: Check the rear rotors and pads, though I looked about 6 months ago
> and they had about 60% wear. If they still have some meat, I will proceed
> directly to step 2.
>
> Step 2: Bleed the entire brake system.
>
> I hope that one of these get it for me. My google searches have mentioned
> bad master cylinders as culprits for soft brakes--any thoughts?
>
> I figured I would post and see if anyone else has had any experiences like
> mine. Cross your fingers that bleeding these lines will do the trick.
>
> ER
>
>
><!-- ~MESSAGE_AFTER~ --> >> Stay informed about: Soft/Spongy Brakes |
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