I had the master cylinder in my 94 Honda replaced just a few months ago
to finally cure a slow fluid leak which was causing my clutch pressure
to drop and the clutch engagement point to fall nearly to the floor
every few months.  Now however, I sometimes have a new problem: after
driving the car for a variable amount of time (usually in heavy LA
traffic where the clutch gets a lot of action), the clutch pressure
will gradually increase to where the pedal becomes somewhat difficult
to press in, and the engagement point is nearly all the way out, away
from the floor.  One time it was so bad that the clutch wouldn't even
fully engage, even with my foot completely off the pedal.  This doesn't
happen all the time, but I'd still like to know what's causing it.
Thanks in advance for any advice.