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
>
>