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Thread: Brake pedal to the floor....

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    NSXPrime Gold warrenw's Avatar
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    Brake pedal to the floor....

    '91 NSX..
    In traffic, Not really to the floor, but with little presure the brake pedal will travel further than with a solid push. Too far to seem normal. To me, this is a brake master cylinder issue. (worn) but the car only has 35,000 miles on it. No brake fluid leaks on the car.
    With a solid brake pedal push, the brakes seem firm as expected.
    Can someone give me feed back on how thier brake pedal is? and if anyone has either rebuilt their master cylinder or replaced it?
    Warren Woodcox
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    Charter Silver EdinKali's Avatar
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    Re: Brake pedal to the floor....

    Sounds like a master cyl. to me too. Age plays a part as well as mileage. Likely that the seals are starting to go in the master cyl. My pedal is firm whether or not I press it slow or fast.
    1992 NSX 5spd/2006 Mazda5 5 spd/2008 Kawasaki Ninja 250R/1989 Yamaha TZR-250 two-stroke


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    Charter Silver pgilliam1's Avatar
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    Re: Brake pedal to the floor....

    No leaks = +1 on master cylinder. Mine did the same thing. Buy it rebuilt or new, don't try to rebuild it yourself. Replacement is an easy DIY on these cars. Some guys say no need to bench bleed them before install, but I always do because it's easy. Save yourself some headaches and get a set of speed bleeders. For some reason air in this system can be a real PITA to get it all out. The pedal should be firm no matter how hard you step on it. Happy Motoring!
    Last edited by pgilliam1; 05-18-2010 at 20:29. Reason: typo

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    Re: Brake pedal to the floor....

    I would say Brake Master Cylinder is the most likely issue as well. During slow applies (< 1 mm/s at the master cylinder, < 4 mm/s on the pedal) the master cylinder primary and secondary pressure seals are not energized as rapidly as during faster applies. If there is a small defect in the lip of either pressure seal it will provide a leak path internally. This will cause the bake pedal to travel further to achieve the target pressure. This can also happen if there is a defect (scratch) in the bore of the master cylinder. I do not recommend rebuilding the master cylinder with new seals because if it is the bore that is the issue you will eventually damage the new seals and be back in the same situation in the very near future.
    1991 NSX (Sold)

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    Charter Champion Larry Bastanza's Avatar
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    Re: Brake pedal to the floor....

    Have you had your brakes bled recently?

    How old is the fluid?

    I would agree it is the master cylinder.

    Regards,
    LarryB

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    NSXPrime Gold warrenw's Avatar
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    Re: Brake pedal to the floor....

    Larry very good questions. I was thinking bleeding was worth a try. The brake fluid is at least 12 years old and the brakes have not been bled since 1999.
    I will bleed, change the fluid and report back.
    Warren Woodcox
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    Registered User Sulley's Avatar
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    Re: Brake pedal to the floor....

    I think LarryB was asking about recent brake bleeding because the seals can be damaged by the crud that builds up in the cylinder bore at full travel of the pedal.

    The master is leaking internally as previously mentioned. Trying to bleed it is wasting your time and money. Get a new one and then bleed the system.

    John

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    Charter Silver pgilliam1's Avatar
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    Re: Brake pedal to the floor....

    Quote Originally Posted by warrenw View Post
    Larry very good questions. I was thinking bleeding was worth a try. The brake fluid is at least 12 years old and the brakes have not been bled since 1999.
    I will bleed, change the fluid and report back.
    It helps the entire system (calipers, master cylinder, ABS, etc.) to bleed it every year. It's cheap maintenance compared to part replacement (for track use we bleed the system no more than 2 weeks before tracking due to moisture contamination). If you'd have done this, the probability of a malfunction of any fluid holding part in your brake system would be greatly reduced, especially at your mileage. Happy Motoring!

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    NSXPrime Gold warrenw's Avatar
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    Re: Brake pedal to the floor....

    With the help of friend, I bled the entire systems today. (replaced all brake fluid)
    Air bubbles in the front, the rear were good.

    Also replaced the pads all around.
    Tested the brakes once done. Had a chance to test the ALB as well. All good.

    The pedal feels good an firm. No issues yet. I will keep an eye on how the brakes perform and if the pedal travel increases.

    Thanks everyone who chimed in!
    Warren Woodcox
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    '09 Toyota Tacoma; '06 Nissan X-Trail

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    Charter Platinum mickeylex's Avatar
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    Re: Brake pedal to the floor....

    Quote Originally Posted by warrenw View Post
    The pedal feels good an firm. No issues yet. I will keep an eye on how the brakes perform and if the pedal travel increases.

    Thanks everyone who chimed in!
    Are the brakes still working well after you bled them? Wondering if I should try that or just go ahead and replace the MC.

    Earlier today, I had the pedal to the floor issue. Pedal slowly went almost to the floor at a stop. Didn't happen in the morning when it was about 60 degrees out, but did happen later when it was above 90 degrees.
    --mickeylex

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    Registered User eddie_82's Avatar
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    Re: Brake pedal to the floor....

    Yup, this is your master cylinder on the way out. I had the same problem occur two weeks ago (pedal sinks when you're at a stop). We tried bleeding all four corners but the problem came right back.

    A friend and I swapped the master cylinder out then re-bled the whole system in my driveway yesterday and for now it appears to have solved the problem. Changing the master cylinder is a very straightforward job and shouldn't take more than 2-3 hours including a full bleed of the system with a friend helping out.

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    NSXPrime Gold warrenw's Avatar
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    Re: Brake pedal to the floor....

    Quote Originally Posted by mickeylex View Post
    Are the brakes still working well after you bled them? Wondering if I should try that or just go ahead and replace the MC.

    Earlier today, I had the pedal to the floor issue. Pedal slowly went almost to the floor at a stop. Didn't happen in the morning when it was about 60 degrees out, but did happen later when it was above 90 degrees.
    Nope, the pedal still goes to the floor on hot days.
    the new Master Cylinder is on the work bench waiting to be replaced.
    The pedal to the floor only happens once the system gets warm. Short trips and on cool days, it isn't an issue. Hot days, Not recommended to to drive the car.

    EDIT:
    Master Cylinder replaced, brakes bled, all is good. (master cylinder is an easy do it yourself; 15 min)
    Last edited by warrenw; 07-11-2010 at 21:59.
    Warren Woodcox
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    '02 Suzuka Blue / Blue S2000; '91 Formula Red / Black NSX
    '09 Toyota Tacoma; '06 Nissan X-Trail

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    Registered User kookoo4nsx's Avatar
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    Re: Brake pedal to the floor....

    Any idea of the cost for the dealer or independant mechanic to do this?

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    Charter Champion Big_D's Avatar
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    Re: Brake pedal to the floor....

    Wow 12 year old brake fluid Remember that you are supposed to replace your brake fluid every 3 years!!! Over time the fluid absorbs moisture and the boiling temp is therby reduced.
    '91 Berlina / Black (Sold)... '06 -'10 were 4 years of NSX Bliss
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    Re: Brake pedal to the floor....

    i will usually bleed my brakes before AND after a good solid track weekend...just to make sure that i'm safe to go around town....aaaaand on track maybe i'm too cautious

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    Re: Brake pedal to the floor....

    SAD Face, mine just started doing this.(pedal slowly goes to the floor at a light) I just had the brake fluid changed last Nov. Do I need a bleeder for this or change out the brake fluid again? Going to order the BMC here in a couple weeks.
    "Beginners can drive fast in a straight line. Mediocre drivers can master the corners, but truly advance drivers make their own lines to get ahead" -R. Takahashi-

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    Registered User eddie_82's Avatar
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    Re: Brake pedal to the floor....

    Quote Originally Posted by Nukem View Post
    SAD Face, mine just started doing this.(pedal slowly goes to the floor at a light) I just had the brake fluid changed last Nov. Do I need a bleeder for this or change out the brake fluid again? Going to order the BMC here in a couple weeks.
    The brake system will need to be bled again after changing the master cylinder. It is also very important that you properly bench-bleed the master cylinder before connecting it to the lines.

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