Soft brake persists after Brake Fluid Flush.

wrote:
> Hello all,
>
> Now that summer is here and temperatures are rising above 90 (in this
> part of Maryland), I have been noticing a peculiar problem with my '92
> Honda Accord. Especially on a hot day (though I am not sure about this
> correlation) after the car's been driven around for a bit, the brake
> pedals tend to get soft. Rather, at high speeds braking slows the car
> down. . . but the application of a persistent pressure causes the pedal
> to keep getting depressed without noticeable braking action. Pumping
> the brake resumes braking, and then it goes soft again until one
> releases and depresses the brake once more. The brake appears to work
> better during the initial braking action, and then gets soft after it
> has been depressed for a little while. There is no squealing,
> clinking, or any kind of noise or vibration.
>
> After reading these (very helpful) forums, I concluded that this may be
> due to water/gas contamination in my brake line, or a leaky master
> cylinder. I had the brake fluid flushed yesterday, and the entire
> brake system was checked out. There was no apparent leaks anywhere. .
> .and the brake fluid levels have always been constant. Today, I still
> find the same soft brake pedal problem.
>
> It is hard to get advice from car mechanics on this, because the
> problem is moody and sometimes difficult to reproduce. The car starts
> out fine in the morning. What do you guys suggest I do to fix this
> problem?
>
> Sincerely,
>
> Subhamoy.
>
a common symptom of the internal seals wearing is that they develop
grooves in their side wall that fluid can leak around. they work in
hard braking because the pressure deforms the seal for a close fit, and
when pumped, for the same reason, but under gradual braking,
particularly when hot, the symptoms are exactly as you describe.

if your car is an accord, i believe you can get a set of seals. if it's
a civic, you have to get the complete cylinder. either way, need to
take the master cylinder off and do the repair. doesn't take long.

Hello all,

Thank you for all the wonderful advice. Here is a follow up on how
this brake problem was solved.

As before, the problem would not replicate at the mechanics shop. The
consensus on this google-group seemed to be a defective master
cylinder, so I asked the mechanic to replace it. The mechanic told me
that since they hadn't replicated/diagnosed the problem, if the
replacement of the cylinder doesn't fix it, they can't be held liable.
And I agreed.

After replacing the master cylinder, they realized that the pressure in
the hydraulics was not what it should be. . .and an inspection revealed
that one of my front wheel calipers was broken. We fixed that. And
now the car seems to be running perfectly. . .without any issues with
the brakes.

I am still not sure how a defective caliper was undetected for so long.
There was no apparent lowering of my brake fluid levels. And I had my
brake system inspected by this mechanic once during an oil change, once
for a brake fluid flush, and finally for this master cylinder change. .
..every time I had described the problem and asked them to check the
system out. Should I be upset about this? Or is it natural for a
mechanic to miss a defective caliper while doing a brake fluid flush?

Anyway. I landed up paying for both the master cylinder and the
calipers. . .and labor to fix both. I am happy that the car is working
good now and the problem has been solved. Thanks to all of you who
responded to my query. And to others who may be having a soft brake
pedal. . .that tends to give in especially in hot weather. . .my advice
is: check the calipers too.

Sincerely,

Subhamoy.




jim beam wrote:
> wrote:
> > Hello all,
> >
> > Now that summer is here and temperatures are rising above 90 (in this
> > part of Maryland), I have been noticing a peculiar problem with my '92
> > Honda Accord. Especially on a hot day (though I am not sure about this
> > correlation) after the car's been driven around for a bit, the brake
> > pedals tend to get soft. Rather, at high speeds braking slows the car
> > down. . . but the application of a persistent pressure causes the pedal
> > to keep getting depressed without noticeable braking action. Pumping
> > the brake resumes braking, and then it goes soft again until one
> > releases and depresses the brake once more. The brake appears to work
> > better during the initial braking action, and then gets soft after it
> > has been depressed for a little while. There is no squealing,
> > clinking, or any kind of noise or vibration.
> >
> > After reading these (very helpful) forums, I concluded that this may be
> > due to water/gas contamination in my brake line, or a leaky master
> > cylinder. I had the brake fluid flushed yesterday, and the entire
> > brake system was checked out. There was no apparent leaks anywhere. .
> > .and the brake fluid levels have always been constant. Today, I still
> > find the same soft brake pedal problem.
> >
> > It is hard to get advice from car mechanics on this, because the
> > problem is moody and sometimes difficult to reproduce. The car starts
> > out fine in the morning. What do you guys suggest I do to fix this
> > problem?
> >
> > Sincerely,
> >
> > Subhamoy.
> >
> a common symptom of the internal seals wearing is that they develop
> grooves in their side wall that fluid can leak around. they work in
> hard braking because the pressure deforms the seal for a close fit, and
> when pumped, for the same reason, but under gradual braking,
> particularly when hot, the symptoms are exactly as you describe.
>
> if your car is an accord, i believe you can get a set of seals. if it's
> a civic, you have to get the complete cylinder. either way, need to
> take the master cylinder off and do the repair. doesn't take long.

wrote:
> Hello all,
>
> Thank you for all the wonderful advice. Here is a follow up on how
> this brake problem was solved.
>
> As before, the problem would not replicate at the mechanics shop. The
> consensus on this google-group seemed to be a defective master
> cylinder, so I asked the mechanic to replace it. The mechanic told me
> that since they hadn't replicated/diagnosed the problem, if the
> replacement of the cylinder doesn't fix it, they can't be held liable.
> And I agreed.
>
> After replacing the master cylinder, they realized that the pressure in
> the hydraulics was not what it should be. . .and an inspection revealed
> that one of my front wheel calipers was broken. We fixed that. And
> now the car seems to be running perfectly. . .without any issues with
> the brakes.

well, if you could gently push the pedal to the floor, the master
cylinder seal /was/ starting to leak. if you had a broken caliper as
well, it's shocking your shop did not detect the problem earlier, but
there's no reason you can't have both problems together. in terms of
costs, you're now set for about 10 years of utterly reliable service, so
i wouldn't sweat it. if you're using dot3 fluid like it says in the
honda manual, make sure it gets flushed annually - fresh fluid contains
rubber preservatives that keep the seals in good condition.

>
> I am still not sure how a defective caliper was undetected for so long.
> There was no apparent lowering of my brake fluid levels. And I had my
> brake system inspected by this mechanic once during an oil change, once
> for a brake fluid flush, and finally for this master cylinder change. .
> .every time I had described the problem and asked them to check the
> system out. Should I be upset about this? Or is it natural for a
> mechanic to miss a defective caliper while doing a brake fluid flush?
>
> Anyway. I landed up paying for both the master cylinder and the
> calipers. . .and labor to fix both. I am happy that the car is working
> good now and the problem has been solved. Thanks to all of you who
> responded to my query. And to others who may be having a soft brake
> pedal. . .that tends to give in especially in hot weather. . .my advice
> is: check the calipers too.
>
> Sincerely,
>
> Subhamoy.
>
>
>
>
> jim beam wrote:
>
wrote:
>>
>>>Hello all,
>>>
>>>Now that summer is here and temperatures are rising above 90 (in this
>>>part of Maryland), I have been noticing a peculiar problem with my '92
>>>Honda Accord. Especially on a hot day (though I am not sure about this
>>>correlation) after the car's been driven around for a bit, the brake
>>>pedals tend to get soft. Rather, at high speeds braking slows the car
>>>down. . . but the application of a persistent pressure causes the pedal
>>>to keep getting depressed without noticeable braking action. Pumping
>>>the brake resumes braking, and then it goes soft again until one
>>>releases and depresses the brake once more. The brake appears to work
>>>better during the initial braking action, and then gets soft after it
>>>has been depressed for a little while. There is no squealing,
>>>clinking, or any kind of noise or vibration.
>>>
>>>After reading these (very helpful) forums, I concluded that this may be
>>>due to water/gas contamination in my brake line, or a leaky master
>>>cylinder. I had the brake fluid flushed yesterday, and the entire
>>>brake system was checked out. There was no apparent leaks anywhere. .
>>>.and the brake fluid levels have always been constant. Today, I still
>>>find the same soft brake pedal problem.
>>>
>>>It is hard to get advice from car mechanics on this, because the
>>>problem is moody and sometimes difficult to reproduce. The car starts
>>>out fine in the morning. What do you guys suggest I do to fix this
>>>problem?
>>>
>>>Sincerely,
>>>
>>>Subhamoy.
>>>
>>
>>a common symptom of the internal seals wearing is that they develop
>>grooves in their side wall that fluid can leak around. they work in
>>hard braking because the pressure deforms the seal for a close fit, and
>>when pumped, for the same reason, but under gradual braking,
>>particularly when hot, the symptoms are exactly as you describe.
>>
>>if your car is an accord, i believe you can get a set of seals. if it's
>> a civic, you have to get the complete cylinder. either way, need to
>>take the master cylinder off and do the repair. doesn't take long.
>
>