Brake problem

This just started : I go to brake and the pedal is hard to push and only goes halfway down without really engaging the brakes. I had to put out in low to slow down and pull over it's fricking scary . then they go back to normal . I do know my front drivers pads are telling me they need changed by the scrapping sound on the rotor. 1999 4runner

 

Sounds like a bad brake booster. Not sure if it's part of the MC on these cars.

 

change the brakes pretty much now....could well be the brake booster too but if they're scraping, ya need to address that now before you get killed.
I'm not trying be a smart-a$$, just want you to be safe