I have a 2004 Monte Carlo with a soft brake pedal. I changed the brakes and bled the lines and it is still soft. Any thoughts?

rotors need replacement

Sounds like a master cylinder problem.

1-change brake master cylinder it has damage o rings that losses break due to its age

2-also try to check all hoses pipes for break oil leak include under car pipes that connect master cylinder to the rear wheels

3-check pressure pipes that connect master cylinder to cylinder head

regards

check the brake fluid level, this is under the hood near the back wall by the drivers side. brakes are serious problem and should go to shop, they probably need the brake bled, this is where all the air is pushed out of the lines, sometimes you can get lucky and pump the brake pedal ( push down and release the brake pedal) over and over again and see if they tighten up

hope this helps

You will need to bleed the brake system. I would start with the rear brakes lines and work towards the front.You must have key off engine off when bleeding brakes, apply pressure on brake pedal 10 times and hold. The brake line is now ready to be open. Open and let the stream of fluid come out and close the line tight. Then release brake pedal once bleeder screw is close. This procedure must be repeated twice front and back. After, brakes have been bleed pump the brake pedal before putting in drive.
Note: Don't let the resevoir run low on brake fluid. This will cause air bubbles to accumulate on the brake system. Always top off before opening bleeder screw.

have the brakes bled and checked for a sticking caliper or bad flexible hose leading to the caliper.

If the brake pedal goes to the floor you need a new mastercylinder so have that changed and bleed the brake system,that should fix your brake problem.

you need to get the brakes bled by a mechanic

Faulty master cylinder.The fluid should be changed before changing the cylider,

if you bleed it wrong you can collapse a seal in the master cylindar .. ...