I recently got a 2.2 cavalier and the guy said brake lines needs fixed so I put fluid in master cylinder and pumped brakes they go straight to the floor I did that a few times and went to check it out no leaks but the master cylinder is still full of fluid idk what it could be any ideas??

 

Air in the lines, bad lines, bad seals. Just putting BF in the MC isn't going to take the air out.

 

I agree, there is air in the lines and master cylinder. Bleed the brakes and then look for leaks. There has to be a reason for the master cylinder being out of fluid.

 

The master cylinder is not out of fluid the fluid stays in the mc

 

You said you put fluid in the master cylinder. Even if it wasn't empty it still has air in the system and needs to be bled.