Mushy brakes 97 riv sc

[Sigsmaster]

I got a 97 riv SC and recently when you would first push on the brakes they were soft. Well imagine my surprise they got worse when I failed to do anything about right away. So now there is almost nothing there when I push the pedal all the way to the floor. So opened the hood checked the resvoir and she was pretty low. I put more fluid in but no better. I asked some buddies way smarter than I if it was possible that I sucked some air in from the low resvoir. That put me at ease and said it would have to be lower than I described. Pads are still good. No leaks, bulging lines or contamination. So another smart guy came by and said 99.8 percent of the time it's the master cylinder. I have the factory manuals but Im just looking for more reassurance before I spend the money. Any more advise?
Bryan

[Sigsmaster]

COME ON! 67 views and no advice? Could someone tell me that I'm more than likely right about the master cylinder before I spend $100 and find out that, thats not the problem? It's ok you can call me a dumb rookie. I just need some reassurance. Thanks everyone I really do appreciate the help.

[gmtech1]

OK, If you are positive there are no external leaks from lines or calipers the problem is most likley internal leaking in the master cylinder.

[Tech II]

And you could still have air in the system too......I'd go with the M/C(no fluid on the booster?)......if you have abs, you need a scan tool to get rid of all the air after a manual bleed.....

[Sigsmaster]

Sure enough it turned out to be the master cylinder. Replaced it and bleed lines following manual and all is fine. The Rivi lives again. Now if I could find out the problem with the intake I would be really happy.