PatrickGSR94

iTrader: (1)

Ever since I flushed my brake fluid over spring break, at random times when sitting at a stop light or something, my brake pedal will start sinking while my foot is on it. Usually if I release the brake and apply it again, it will feel normal. Other times it will also feel normal. If the problem is the master cylinder, why would it only happen sometimes instead of all the time?

JimBlake

I bet it's gonna happen more & more often as it gets warmer.

Mine did that, I tried bleeding it a couple times, but it kept coming back. Get ready to replace the master cylinder...

Kusai.Nihonjin.Desu

If you JUST flushed your brake fluid, you might want to try bleeding it again, you might have some air pockets.

If this persists, your master brake cylinder is going bad. But I have a feeling you might just need to bleed'em since you didnt have the problem prior to the brake fluid flush.

ubreak_ubuy

it used to happen to me only when i had my ac on. weird. but after i replaced my master cylinder, it went away...

shamoo

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by raceinspired &raquo;</TD></TR><TR><TD CLASS="quote">it used to happen to me only when i had my ac on. weird. but after i replaced my master cylinder, it went away...</TD></TR></TABLE>

I think it's normal. My parent's Honda (brand new) as well as both of my previous Hondas (also new when it happened) did this too.

Since part of the system has something to do with vacuum pressure, and that changes sometimes during load (i.e.: with A/C on), your pedal pressure might change.

This is a guess, but I'm pretty confident that it's normal. It's happened on all our cars when they were new.

milo

i would try to bleed the brakes again. after making sure that all bubbles are gone, step on the brake pedal several times then hold it; wait several seconds-if the pedal goes to the floor then its your MC. goodluck

..::91TEG-G2::..

i had that same problem on my DA.. and that problem was, the gaskets that keep the fluid in the lines.. was going out, so i had to replace it.. went to autozone and got one for free, only cuz my uncle buys alot of ish there for his work, so he gets mad discounts.. but we put the new MC in and it works fine.. bled the breaks and walla... firm pedal again..

PatrickGSR94

iTrader: (1)

oh shoot I forgot to say, I did bleed the brakes again, and no bubbles came out, only clean fluid.

I should also say that it's not normal, because I never had this problem before flushing the fluid (first time I've ever flushed the fluid, and I've had the car for over 70K miles now ).

I have had a very very slight miniscule leak from the master cylinder (the paint on the booster below the MC is bubbling and flaking off), so do you think maybe the repeated operation of the brakes during the flushing/bleeding process just finished off the MC seals or something? I know I need a new MC.

JimBlake

Some people say don't stroke the pedal all the way down when bleeding the brakes. The last 1/3 of the piston stroke kicks up crud that can damage the seals.

70k is a long time to go between brake fluid flushing. At least every 2 years, then you don't have so much crud in the first place.

PatrickGSR94

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">70k is a long time to go between brake fluid flushing. At least every 2 years, then you don't have so much crud in the first place.
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yeah I know, I just never got around to it before... the stuff that came out was NASTY, somehow I doubt it had ever been changed before (160K miles at the time)

anarchyfox

damn...i'm having this problem...ugh. i hate brake fluid.

mickey513

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">I bet it's gonna happen more & more often as it gets warmer.

Mine did that, I tried bleeding it a couple times, but it kept coming back. Get ready to replace the master cylinder...
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Yup, EXACT samething happen to me. This occured after I bled the brake system. At first I thought I did it wrong and got air in but I bled in again and the exact samething. Just get a new master cylinder and your problems will go away.