I have to disagree, even though what you say is true.

I bet it is your MC. I just replaced mine on my 91 Prelude
and when it got hot out, the pedal sinking was much more
common.

Easy fix, did it myself, new (not rebuilt) MC from a local
import parts shop was $70. I would not pay the OEM
cost.

Bench bleed the MC, bleed all 4 lines. You'll end up with
a new MC, new brake fluid, and a pedal that won't sink
to the floor anymore when the temperature rises.

"E. Meyer" <e52.meyer0SPAM@ieee.org> wrote in message
news:BD3D071C.93750%e52.meyer0SPAM@ieee.org...
> 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.
>
> Also check the condition of the pads and calipers at the wheels to make
sure
> you don't have a binding caliper creating excessive heat and wear. The
> easiest check is to swing open the caliper as if changing the pads and
> verify that the caliper pins slide in and out freely.
>
> On 8/9/04 6:20 AM, in article haneh0dicpao1unqammi07coap4codkomv@4ax.com,
> "Nick" <npolite@NOSPAMMONKEYS.yahoo.com> wrote:
>
> > One additional thing I forgot to mention was that I have replaced the
> > reservoir fluid 3 times by siphoning it out without any luck. Also, I
> > haven't needed to refill the reservoir so I don't think that there is
> > a leak in any of the lines.
> >
> > Thanks,
> > 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
> >
> >
>