Soft brake persists after Brake Fluid Flush.

Discussion in 'General Motoring' started by subhamoy, Jun 10, 2005.

  1. subhamoy

    subhamoy Guest

    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


    subhamoy, Jun 10, 2005
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  2. subhamoy

    Jason Guest

    You may be right. I suspect the fluid is contaminated or has broken down
    or there may be air in the lines. Regardless, the best solution would be
    to drain out all of the brake fluid and replace it with new fluid. If you
    have never done it before--I advise you to take it to a mechanic that you
    trust and have them do it. Mechanics have all of the tools and equipment
    to make the job much easier and quicker. It's a messy job.
    Jason, Jun 10, 2005
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  3. subhamoy

    chris24ali Guest

    Sounds like the problem I had with my 88 accord. Soft brakes when
    everything got hot. It got so bad for me that I had to change the
    master cylinder, and both wheel cylinders along with flush and bleeding
    of the brake system.

    But even with all that It didn't help things much. To me all honda's
    feel this way. I now have an 2005 odyssey and the first thing I
    noticed upon driving it was the soft brakes. Nothing like the old
    accord but soft. I drove a number of Nissan's and every one of those
    cars had brakes that would bring the car to a halt at the lightest
    touch of the pedal.
    chris24ali, Jun 10, 2005
  4. I would have guessed:

    80% probability: master cylinder
    15% probability: contaminated brake fluid
    5% probability: something else

    You eliminated the easy one. I think you need to do the master
    cylinder now.
    Gordon McGrew, Jun 10, 2005
  5. subhamoy

    Nightdude Guest

    Same thing happening with my Acura Vigor. It gets worse if I run the A/C, as
    it probably heats things up much more in the engine bay. I will be changing
    the master cylinder and the hoses also (as a precaution).

    I would do the master cylinder myself, as it looks simple enough in the
    helms book, but it's just too damn messy and I don't want to work in 90F
    humid weather.
    Nightdude, Jun 10, 2005
  6. I should have mentioned in the previous post that the leak in the MC
    is internal. You won't see any fluid on the garage floor.
    Gordon McGrew, Jun 10, 2005
  7. I agree. My wife's 92 Acura Legend had that problem and new master cylinder
    fixed it.
    Mike Iglesias, Jun 10, 2005
  8. subhamoy

    hiptech Guest

    The symptoms you describe are of a failing power brake master cylinder.
    I know as this has happened to me on my '89 and '93 Accords.

    I strongly suggest you have this attended to ASAP, as brake failure
    could be imminent. The valve inside the cylinder is deteriorating and
    when it goes say goodbye to your brakes!

    As for repeatabilty of the symptoms, don't worry, it will definitely be
    getting worse and start occuring more frequently. The problem is, you
    don't know when it will eventually fail and the results could be

    If you don't have a reliable mechanic, I have some suggestions:
    1. Honda dealer
    2. Independent Honda mechanic (in the phone book)
    3. Car - MechanXfiles - database of over 16,000 mechanics,
    recommended by members -
    4. Helm service manual if you feel capable of doing it yourself?

    Either way, don't wait, your '92 Accord is an accident waiting to
    hiptech, Jun 10, 2005
  9. When you say hot, do you mean from heavy braking such as going down
    hills? Or do you mean city driving on a hot summer day?

    The typical symptom of MC failure (in Hondas at least) is a hot summer
    day, sitting at a stop light and suddenly the pedal sinks to the
    floor. Pump it once or twice and it may be fine for a while.

    Softness after heavy use sounds like the brake fluid is boiling due to
    contamination, a mechanical problem or simple over use. It could also
    be caused by a frozen caliper or similar problem which causes the
    brake to be always applied. This is easy to recognize because one (or
    more) wheels will be hot as a branding iron, even though you haven't
    been braking much at all.
    I would consider that to be over-boosted, but you can probably adapt
    to anything. If you are used to one, the other is going to feel
    Gordon McGrew, Jun 10, 2005
  10. subhamoy

    chris24ali Guest

    Definately hot summer day driving in the big city. I remember flushing
    the system and finding fluid that was water like and dirty as hell.
    I'm sure I didn't get out all and probably ended up contaminating the
    new fluid.
    chris24ali, Jun 10, 2005
  11. subhamoy

    jim beam Guest

    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.
    jim beam, Jun 11, 2005
  12. subhamoy

    subhamoy Guest

    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.


    subhamoy, Jun 17, 2005
  13. subhamoy

    jim beam Guest

    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.
    jim beam, Jun 18, 2005
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