my calipers make a weird crunching noise when i press the pedal hard. do i need to rebuild them?

 

you need to jack up the car and take a look at your calipers, pads and rotors first.

 

You probably have some grit between the backs of the pads and the pistons. If your calipers have anti-rattle shims between the pads and pistons they could be dirty as well. Pull the pads, clean the backs of them and the fronts of the pistons up and see if that fixes you.