Soft brake persists after Brake Fluid Flush.

Hello all,

Now that summer is here and temperatures are rising above 90 (in this
part of Maryland), I have been noticing a peculiar problem with my '92
Honda Accord. Especially on a hot day (though I am not sure about this
correlation) after the car's been driven around for a bit, the brake
pedals tend to get soft. Rather, at high speeds braking slows the car
down. . . but the application of a persistent pressure causes the pedal
to keep getting depressed without noticeable braking action. Pumping
the brake resumes braking, and then it goes soft again until one
releases and depresses the brake once more. The brake appears to work
better during the initial braking action, and then gets soft after it
has been depressed for a little while. There is no squealing,
clinking, or any kind of noise or vibration.

After reading these (very helpful) forums, I concluded that this may be
due to water/gas contamination in my brake line, or a leaky master
cylinder. I had the brake fluid flushed yesterday, and the entire
brake system was checked out. There was no apparent leaks anywhere. .
..and the brake fluid levels have always been constant. Today, I still
find the same soft brake pedal problem.

It is hard to get advice from car mechanics on this, because the
problem is moody and sometimes difficult to reproduce. The car starts
out fine in the morning. What do you guys suggest I do to fix this
problem?

Sincerely,

Subhamoy.