I own a 2006 cobalt ss and recently I've been losing brake fluid slowly but no visible leaks. I'm experiencing a soft clutch that sometimes changes sweet spot if I drive it enough, also my brakes feel soft. Is this a sign of a bad master cylinder?

 

Sounds like you may be getting air into the system.

 

^This...I would visually check all the connections and make sure there nice and tight.

If its faulty and there is no leak then it is leaking internally by the seals.

 

That was my first thought, but I had my slave cylinder and clutch replaced last month and they vacuum bled the whole system and told me they couldn't find any air in the lines. So my last thought is the master cylinder has a leak so its getting air in the whole system and making it so I'm not getting pressure in the reservoir.

 

I have a master if you wanna buy it. From an 06 lsj, 66k miles.

 

I got dez cheezburgahs man!

 

I would contact slowbalt for a new master, Also I am unsure if you have a 2.4 or a 2.0 ss, But since your cars is manual you will need a master cylinder that is for a manual transmission not automatic

You are technically kinda right but it won't be sucking in air, The seal around the piston is leaking and as you accumulate pressure it leaks by the piston seal and back into the reservoir resulting in a loss in pressure.