a 1987 Chevy Caprice.? When i'm driving, and i go to brake, my brakes harden or stiff up to where i have to push down really hard in order for my car to come to a complete stop. I don't know what's wrong.
Yes the brake power booster is bad. It will cause engine problems as well.
I change one for a customer of mine not only was it doing as you described but it also caused his engine idle rpm to increase. I changed the booster and solved both of his problems.
It is pretty simple to change, may take you about 1 1/2 to 2 hours to do.