Appreciate opinions on brake issue
 

Hello, I have a 08 CX-7, with 98,000 miles. Love this car!! I have noticed thru the last 6 months, that on rare occasions, always when sitting at a stop light, or stuck in heavy traffic that is not moving...the brake
peddle seems to travel towards the floor by maybe 1/2". Have had it to my Mazda dealer (love Power Mazda in Salem, Or)...and they can't figure out what it is exactly. I left it with them for the day, and after
driving it around off and on thru the day, they could not get the car to repeat the issue.

Took it home, and have begun to notice that perhaps it's doing it a little more often than it used to.

Power Mazda said it might be one or both parts of the master cylinder. It never happens while just braking to come to a stop, only after you sit at a stop light for a bit, and then only on an irregular basis.

Just wondering if anyone has had a problem like this, and if so, what it turned out to be. I'm about ready to go ahead and tell them to do the m.c. just to be on the safe side.

Thanks for any help.

Jan