There's only two things it could be: the brake cylinder or the hose. It's probably the brake cylinder, and those are easy to replace: jack up the car and put it on a jackstand, remove the wheel, then the brake drum followed by the shoes. Remove and replace the brake cylinder, reassemble the brake, bleed the system (you should only have to bleed the passenger front and driver rear since they're completely separate from the driver front and passenger rear due to the "dual diagonal" brake system cars have) and put the wheel back on.
The 2001 Buick Century brake light switch is located beneath the dashboard, on the drivers side. The brake light switch should be labeled as such.
I would replace the line....ughh
Have you checked the fuses?
Remove the tire, brake caliber and the rotor should side off the hub.
Master cylinder, upper firewall, driver's side.
Make sure the parking brake is completely released. If the parking brake is on the Highlights go off.
I'm going to say there's probably a hole in your brake line.
Your brake master cylinder may be leaking. Have it checked by a technician.
On a1996 Buick Le-sabra it is on the Driver side under hood right below brake fluid reservoir.
The correct size is 3057.
That sounds like a wheel cylinder leaking brake fluid.
master cylinder located at the driver's side firewall - reservoir should be translucent look at side should have max/min. fluid markings or remove cover to observe level