Possible brake problems requiring attention, and their solutions, include:
* Low brake fluid: Check your brake fluid reservoir (usually a clear container near the master cylinder). If it's low, you have a leak somewhere in the system. Do not simply add fluid. Find and repair the leak first. A low fluid level *could* indicate a leak *in* the master cylinder itself, requiring replacement.
* Spongy or soft brake pedal: This could indicate air in the brake lines (requiring bleeding), a worn master cylinder, or a problem with the brake booster.
* Hard brake pedal: This could indicate a problem with the brake booster, a vacuum leak, or a seized caliper.
* Brake failure: This is a serious problem and requires immediate professional attention. Do not drive the car.
What you might be thinking of:
If you're experiencing brake problems *after* some brake work (like replacing calipers, pads, or rotors), you likely need to bleed the brakes. This removes air that may have entered the brake lines during the repair. Bleeding requires two people and a wrench to open the bleed valves at each wheel. There's plenty of information online and in repair manuals on how to bleed brakes on a 1997 Cadillac Deville.
In short: You don't reset a master cylinder. If you have brake problems, diagnose the *cause* of the problem and address that. If unsure, take your car to a qualified mechanic. Brake failure is dangerous.
