When i try to use the brakes my car will slide, or i have to pump the brakes to stop, why?

98 old cutlass, changed brakes, rotors. some1 said may nd to have my brakes bled, but my "mechanic" says he checked them and they don't. some1 else said my brake line may have air, but mechanic says not true. do I need a new mechanic? what else can cause this problem? anti-lock brake system?|||If it were just you having to pump the brakes,I would say it "might" be an anti lock brake sensor at one of the wheels. But since you said that it sometimes slides,.....I take it that you mean one wheel will lock up and skip.If this is the case, then the brakes need bled. Take the car to another "reputable" mechanic and have them bleed the brake system.If this solves the problem,be sure to NEVER go back to the first mechanic again, and be sure to tell all your friends that the first one sucks! GOOD LUCK! Rob in Pa.|||yeah i would say u need a new mechanic, sounds like the brake master cylinder is the culprit and take to auto zone and let them hook 'putor to it to see if any codes for anti-lock system. won't cost anything.|||master cylinder or needs bleeding, anti-lok won't do that, it either works, or it justs stops like normal brakes, get a new mechanic he sounds brain dead or lazy.