when i'm driving and come to a stop sign and i have to step on my brakes for a while, my brakes will slowly start to sink down, and if i let it go and do it agian, it'll keep on doing the same thing, what could be wrong?

 

Is the brake fluid in the master cylinder low? If so, check for leaks around the master cylinder, front calipers, and rear wheel cylinder. Replace the leaking component and then thoroughly bleed the brakes.

If no leak is found, the master cylinder may be bad. Replace and bleed system.

 

fluid is good, and no leaks at all whatsoever. master cylinder, i'll replace and rebleed to see what happens.

 

If you can't find a leak then I should have suggested that you first try bleeding the system of air. If this doesn't fix the problem, then replace the master cylinder and rebleed.