Okay, so a friend of mine's brake system just got recently bled and now, he says that when he's holding down the brake pedal, ex. at a stop light, it would start to sink to the floor. He drives an automatic and says it happens in D and N. Does anyone know why the pedal would sink a short while after it's being held?

 

Bad M/C

 

That's what I was starting to think. Anyone else think otherwise or same?

 

Had the exact same problem. your master cylinder needs to be changed.

 

put in stainless lines. bled. didnt feel right. bled again. didnt feel right. one more time. gave up.took to mechanic friend. master cylinder fried. your symptoms sound like mine did.

 

if it didnt do it before then u didnt bled the brakes right. if not get a new MC

 

a little is normal. its the vaccum level and idle changing. if it is a lot, then check the m/c for vaccum leaks. plug all the holes and vaccum test it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by littleredcivic &raquo;</TD></TR><TR><TD CLASS="quote">a little is normal. its the vaccum level and idle changing. if it is a lot, then check the m/c for vaccum leaks. plug all the holes and vaccum test it.</TD></TR></TABLE>

How do I conduct a vacuum leak?

 

You have to put a T in the vacuum line, them hook up a gauge with the car off put a sucktion on it and see if it holds or not.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by littleredcivic &raquo;</TD></TR><TR><TD CLASS="quote">a little is normal. its the vaccum level and idle changing. if it is a lot, then check the m/c for vaccum leaks. plug all the holes and vaccum test it.</TD></TR></TABLE>

The pedal should hold even. It should not sink slowly to the floor as he decribed. The seals in the master cylinder are leaking. Either the bore it worn or the seals have worn/tore.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hybrid93Eg &raquo;</TD></TR><TR><TD CLASS="quote">

The pedal should hold even. It should not sink slowly to the floor as he decribed. The seals in the master cylinder are leaking. Either the bore it worn or the seals have worn/tore.
</TD></TR></TABLE>

So replacing the entire Brake MC is the only way to go right?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fms1day &raquo;</TD></TR><TR><TD CLASS="quote">So replacing the entire Brake MC is the only way to go right?</TD></TR></TABLE>

yes. buying the seals, etc to rebuild parts are becoming part of the past, and are dying out. plus, if you replace it, and it has problems, then you are back where you started. if you buy a new one, and it has problems, then you just take it back and get a new one with no extra time spent.

as all parts used to be, you could by a rebuild kit, or a seal kit and do it yourself, but fewer part houses are carrying those items or the manufactor is no longer making them.

it would just be easier to by a new M/C and replace it as a whole then it would be to repair it.

 

yes. replace it. same thing happened in my car. i ignored it nxt thing i knew brake fluid started to leak from the MC.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fms1day &raquo;</TD></TR><TR><TD CLASS="quote">

So replacing the entire Brake MC is the only way to go right?</TD></TR></TABLE>

Now-a-days, yes. You can disect them and rebuild them, but 9 times out of 10, its too late by then. People don't usually notice them failing in the beginning stages. Its usually not caught until the piston has been driven down the cylinder crooked many times and thus destroyed the walls of the cylinder by wearing the aluminum down. You can usually see this starting to happen in the color of the brake fluid. It will get a graphite like color to it. Of course, if your fluid is filty and a million years old to begin with, this can be hard to diagnose.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nello a. &raquo;</TD></TR><TR><TD CLASS="quote">put in stainless lines. bled. didnt feel right. bled again. didnt feel right. one more time. gave up.took to mechanic friend. master cylinder fried. your symptoms sound like mine did.</TD></TR></TABLE>

i did the same exact thing... new ss lines and blew the m/c when bleeding

yeah i would say its the master cylinder, just simply replace it. i got a new one from Honda for 170.00 which i thought was up there in price, but whatever, **** happens right??

 

Thanks guys.

 

theres air in the system because they bled it wrong or either his master cylnder is crapping out. check the brake fluid level first.

 

bad master cylinder

if you have a stock 92-95 get a 91 ex 15/16ths master cylinder

i got mine for like 40 at napa about 1.5 years ago

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bense &raquo;</TD></TR><TR><TD CLASS="quote">
if you have a stock 92-95 get a 91 ex 15/16ths master cylinder
</TD></TR></TABLE>

Explain the reason for this? I know alot of parts are interchangible, but what are the benefits for this?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dohcdelsol &raquo;</TD></TR><TR><TD CLASS="quote">

Explain the reason for this? I know alot of parts are interchangible, but what are the benefits for this?</TD></TR></TABLE>

If your civic didn't have ABS, you have a 13/16" MC. The 91ex sedan came with a 15/16". the larger diameter piston will give you a firmer pedal. It bolts up perfectly to the BB and brake lines.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RTI &raquo;</TD></TR><TR><TD CLASS="quote">If your civic didn't have ABS, you have a 13/16" MC. The 91ex sedan came with a 15/16". the larger diameter piston will give you a firmer pedal. It bolts up perfectly to the BB and brake lines.</TD></TR></TABLE>

sweet deal, learned something new, and will definitely have to save this for later.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RTI &raquo;</TD></TR><TR><TD CLASS="quote">

If your civic didn't have ABS, you have a 13/16" MC. The 91ex sedan came with a 15/16". the larger diameter piston will give you a firmer pedal. It bolts up perfectly to the BB and brake lines.</TD></TR></TABLE>

1). Ex's did not all have ABS. Those have 7/8 or 15/16 cylinders stock in the EG's
2). Only the lower end models have the 13/16 master cylinder
3). What the hell is a "BB" that you are referring to?

 

BB = brake booster

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hybrid93Eg &raquo;</TD></TR><TR><TD CLASS="quote">
3). What the hell is a "BB" that you are referring to?</TD></TR></TABLE>

Brake Booster

EDIT: Refresh owns me.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 94hatchling &raquo;</TD></TR><TR><TD CLASS="quote">

sweet deal, learned something new, and will definitely have to save this for later.</TD></TR></TABLE>

I think he should have clarified. It will move more fluid quicker. Correctly stated, it will make the brakes more responsive, not "firmer". It should be matched with the larger claipers, etc. If you like a REAL sensative pedal, then this is the mod for you. Otherwise, put the stock unit back on and be happy.