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Thread: Brake fade

  1. #1
    Join Date
    May 2009
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    Brake fade

    Hi All,

    Getting my Cobra back on the road and MOT passed but on 2 runs now I am getting some serious brake fade which takes a few pumps to get any effective braking. I think its just the heat on the master cylinder.

    I have wrapped the headers, heat shield between headers and master cylinder as well as heat shield around the resouvir - its better but today in 31 deg heat after 20 miles she was running fine then hit town traffic with a lot of stop start and then the brakes went again.

    Thinking of ducting in fresh air or cutting a hole in the wheel well into the master cylinder area to improve air flow but I think its slow traffic that effects it so maybe adding a fan ?? underside scoops into the header area ???

    Any thoughts or tips appreciated

  2. #2
    Join Date
    Aug 2004
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    I can't see why warming the brake fluid up by a few degrees would cause the brake fade that you are seeing. Maybe it's a symptom of air in the system?
    Cheers

    Myles D-W

  3. #3
    Join Date
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    Quote Originally Posted by mylesdw View Post
    I can't see why warming the brake fluid up by a few degrees would cause the brake fade that you are seeing. Maybe it's a symptom of air in the system?
    Or moisture.
    Cheers, Clive

    (If I'm not here, I'm either in my new workshop or on the golf course!)

  4. #4
    Join Date
    Oct 2018
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    As above. Bleed the old fluid out and try again. If you still have issues then you may have a weak/worn seal in the master cylinder.
    Dax with 1964 Dual Quad 427 and Toploader box

  5. #5
    Join Date
    May 2009
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    Quote Originally Posted by ChrisP View Post
    As above. Bleed the old fluid out and try again. If you still have issues then you may have a weak/worn seal in the master cylinder.

    Brand new brake fluid Dot and its booked in for Saturday for a power bleed to make sure its sorted ! Still makes no sense why it would work for 30 min then disappear on me ??

  6. #6
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    Aug 2004
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    Christchurch, NZ
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    Gas law: a small bubble becomes a large bubble when you heat it up.
    Cheers

    Myles D-W

  7. #7
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    Quote Originally Posted by Sion G WelshV8 View Post
    Brand new brake fluid Dot and its booked in for Saturday for a power bleed to make sure its sorted ! Still makes no sense why it would work for 30 min then disappear on me ??
    No it doesn't! It's normally the other way around. Is it possible you have a very small leak? I once had a similar issue where the brakes would pull left. Turned out it was an invisible leak on the rh hose. Tiny, no noticeable drop in fluid, no fluid visible but changed the hose and it cured it (later tested the pipe with an airline to prove the leak was there).

    Yours is odd. My master cylinder must get very warm as do most I would think but I have never had an issue due to heat. My money is on a leak/bubble or faulty master cylinder seal but will be interested to hear what you find.
    Dax with 1964 Dual Quad 427 and Toploader box

  8. #8
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    May 2009
    Location
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    Mine does pull to the left and have changed a lot of the pipe work......I assumed it was a bleeding issue.

    How did you find out which pipe it was with such a small leak ? Start with the flexi ?

  9. #9
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    Yes, do the flexi. Sometimes they can have a ‘flap’ inside that closes and causes issues too. Change the one on the right first.

  10. #10
    Join Date
    May 2009
    Location
    Blaenau Ffestiniog, N Wales
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    A power bleed and a semi-ceased rear calliper was the issue everyone. A lot of WD40 and removing one pad at a time and getting my son to press the brake and I levered the piston back in repeatedly seems to have done the trick. A new diff next winter will probably be an opportunity to drop the back end and get the callipers refurbished at the same time ! Thank everyone

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