Honda Car Forum

>what my '94 GS-R was like when it failed.
>
> I can confirm that Integras of this vintage had dual fluid systems,
> one for service and one for ABS. Can't explain why right now, guess I
> will study the manual when I get bored.

Agreed. They're separate systems. The early '90's Integra master
cylinders are prone to premature failure, from my experience.

JM

On 8/9/04 1:50 PM, in article 4117c74c.20661564@news.txol.net, "Rex B"
<rex@@txol.net> wrote:

> On Mon, 09 Aug 2004 15:49:01 GMT, "E. Meyer" <e52.meyer0SPAM@ieee.org> wrote:
>
> ||Your symptom sounds more like water in the fluid (it boils when it gets hot
> ||and that changes the braking performance) than a bad master cylinder. Try
> ||bleeding new fluid through the system and out at the wheels to clean out the
> ||lines. If you have ABS, that fluid is separate from the main system and
> ||should also be changed.
>
> Are you saying there are 2 separate fluid circuits for brake and ABS?
> I've not heard of that. Could you explain how that works?
> Texas Parts Guy

I doubt I can explain it very well, but I'll try. There is an eight page
long explanation of it in the FSM.

That generation of Honda has a separate ABS reservoir with a pump that
maintains a high pressure actuator with brake fluid at 3600 PSI. The fluid
in the ABS system never meets the stuff in the main brake lines unless/until
the ABS engages, at which time there is a very small amount of mixing.
Essentially, the fluid in the ABS is used as hydraulic fluid to work the
pistons and valves in the ABS unit.

There is a "cut" valve in the brake lines that is open when the ABS is not
engaged. When the valve is open, the brake lines are straight through from
the master cylinder to the wheels and the brakes function as if there is no
ABS. When the ABS engages, the high pressure fluid maintained in the ABS
unit at 3,600 PSI is ported to the cut valve. The cut valve closes,
blocking the fluid flow from the master cylinder and detouring the
downstream fluid in the brake line into a pressure reduction chamber which
relieves the pressure on the brake, allowing the wheel to turn.

The good part of the system is that if the ABS fails, the main brakes are
unaffected. The bad part is that unless the ABS fluid is routinely changed
and the ABS is periodically exercised (engaged), either the pistons in it
start leaking and it fails or it loses its ability to maintain pressure and
it fails (one or the other of which has happened to every Honda of that
generation I have encountered).

On Sat, 14 Aug 2004 02:46:28 GMT, "E. Meyer" <e52.meyer0SPAM@ieee.org>
wrote:


>
>The good part of the system is that if the ABS fails, the main brakes are
>unaffected. The bad part is that unless the ABS fluid is routinely changed
>and the ABS is periodically exercised (engaged), either the pistons in it
>start leaking and it fails or it loses its ability to maintain pressure and
>it fails (one or the other of which has happened to every Honda of that
>generation I have encountered).

Not my '94 with 126K miles. (knock on aluminum)

Here is an update...


Well I installed a rebuilt MC on Saturday and it wasn't too
hard except for one of the brake lines. In my Hayes manual it states
to hand tighten the bolts that the MC mounts to the brake booster
before reassembling the brake lines. If you do this, you won't be able
to get the one brake line installed. It took me about 1/2 hr to
realize this (at first thinking that the threads were stripped on the
rebuilt MC). What I did to get it on was pull out the MC to the end of
the mounting bolts, angle it a bit and was then able to get the brake
line on. After which everything took less than 5 minutes to install.
Since then it looks like I haven't seen the problem again but
it has only been 2 days so I am hoping for the best.

Thanks again for everyone's help!

Nick

On Mon, 09 Aug 2004 07:10:52 -0400, Nick
<npolite@NOSPAMMONKEYS.yahoo.com> wrote:

>Hello all,
>
> I got a problem which I think is being caused by a failing
>master cylinder but wanted to make sure before I go out and buy one. I
>am noticing that every 5th time that I brake, the brake pedal will go
>down to the floor more significantly than normal. What is odd is that
>this is only occurring when the rotors warm up. In the morning I do
>not notice this, but could also be because of highway driving. Do I
>have a master cylinder which is beginning to fail? Also I see that the
>OEM master cylinder costs about $250 and one from Autozone costs $50.
>Besides that the one from Autozone is a rebuilt one, is there any
>other reason why I should go with OEM?
>
>Thanks in advance for all of your help,
>Nick

On Sat, 14 Aug 2004 02:46:28 GMT, "E. Meyer" <e52.meyer0SPAM@ieee.org> wrote:

||On 8/9/04 1:50 PM, in article 4117c74c.20661564@news.txol.net, "Rex B"
||<rex@@txol.net> wrote:
||
||> On Mon, 09 Aug 2004 15:49:01 GMT, "E. Meyer" <e52.meyer0SPAM@ieee.org>
wrote:
||>
||> ||Your symptom sounds more like water in the fluid (it boils when it gets
hot
||> ||and that changes the braking performance) than a bad master cylinder. Try
||> ||bleeding new fluid through the system and out at the wheels to clean out
the
||> ||lines. If you have ABS, that fluid is separate from the main system and
||> ||should also be changed.
||>
||> Are you saying there are 2 separate fluid circuits for brake and ABS?
||> I've not heard of that. Could you explain how that works?
||> Texas Parts Guy
||
||I doubt I can explain it very well, but I'll try. There is an eight page
||long explanation of it in the FSM.
||
||That generation of Honda has a separate ABS reservoir with a pump that
||maintains a high pressure actuator with brake fluid at 3600 PSI. The fluid
||in the ABS system never meets the stuff in the main brake lines unless/until
||the ABS engages, at which time there is a very small amount of mixing.
||Essentially, the fluid in the ABS is used as hydraulic fluid to work the
||pistons and valves in the ABS unit.
||
||There is a "cut" valve in the brake lines that is open when the ABS is not
||engaged. When the valve is open, the brake lines are straight through from
||the master cylinder to the wheels and the brakes function as if there is no
||ABS. When the ABS engages, the high pressure fluid maintained in the ABS
||unit at 3,600 PSI is ported to the cut valve. The cut valve closes,
||blocking the fluid flow from the master cylinder and detouring the
||downstream fluid in the brake line into a pressure reduction chamber which
||relieves the pressure on the brake, allowing the wheel to turn.
||
||The good part of the system is that if the ABS fails, the main brakes are
||unaffected. The bad part is that unless the ABS fluid is routinely changed
||and the ABS is periodically exercised (engaged), either the pistons in it
||start leaking and it fails or it loses its ability to maintain pressure and
||it fails (one or the other of which has happened to every Honda of that
||generation I have encountered).

Interesting. Sounds like you need to exercise your ABS more often



Texas Parts Guy

On 8/16/04 4:14 PM, in article 41212399.29035966@news.txol.net, "Rex B"
<rex@@txol.net> wrote:

> On Sat, 14 Aug 2004 02:46:28 GMT, "E. Meyer" <e52.meyer0SPAM@ieee.org> wrote:
>
> ||On 8/9/04 1:50 PM, in article 4117c74c.20661564@news.txol.net, "Rex B"
> ||<rex@@txol.net> wrote:
> ||
> ||> On Mon, 09 Aug 2004 15:49:01 GMT, "E. Meyer" <e52.meyer0SPAM@ieee.org>
> wrote:
> ||>
> ||> ||Your symptom sounds more like water in the fluid (it boils when it gets
> hot
> ||> ||and that changes the braking performance) than a bad master cylinder.
> Try
> ||> ||bleeding new fluid through the system and out at the wheels to clean out
> the
> ||> ||lines. If you have ABS, that fluid is separate from the main system and
> ||> ||should also be changed.
> ||>
> ||> Are you saying there are 2 separate fluid circuits for brake and ABS?
> ||> I've not heard of that. Could you explain how that works?
> ||> Texas Parts Guy
> ||
> ||I doubt I can explain it very well, but I'll try. There is an eight page
> ||long explanation of it in the FSM.
> ||
> ||That generation of Honda has a separate ABS reservoir with a pump that
> ||maintains a high pressure actuator with brake fluid at 3600 PSI. The fluid
> ||in the ABS system never meets the stuff in the main brake lines unless/until
> ||the ABS engages, at which time there is a very small amount of mixing.
> ||Essentially, the fluid in the ABS is used as hydraulic fluid to work the
> ||pistons and valves in the ABS unit.
> ||
> ||There is a "cut" valve in the brake lines that is open when the ABS is not
> ||engaged. When the valve is open, the brake lines are straight through from
> ||the master cylinder to the wheels and the brakes function as if there is no
> ||ABS. When the ABS engages, the high pressure fluid maintained in the ABS
> ||unit at 3,600 PSI is ported to the cut valve. The cut valve closes,
> ||blocking the fluid flow from the master cylinder and detouring the
> ||downstream fluid in the brake line into a pressure reduction chamber which
> ||relieves the pressure on the brake, allowing the wheel to turn.
> ||
> ||The good part of the system is that if the ABS fails, the main brakes are
> ||unaffected. The bad part is that unless the ABS fluid is routinely changed
> ||and the ABS is periodically exercised (engaged), either the pistons in it
> ||start leaking and it fails or it loses its ability to maintain pressure and
> ||it fails (one or the other of which has happened to every Honda of that
> ||generation I have encountered).
>
> Interesting. Sounds like you need to exercise your ABS more often
>
>
>
> Texas Parts Guy

If you have one of these you do. Most people found that out after the
failure though.