If your Honda Civic is having brake problems, you should not drive the car until you get it all sorted out. Brake problems are very serious and could cause a car accident. Because there are a few different common problems that can occur with the Civic's brakes, you need to do some troubleshooting to try to figure out what could be causing your brake problems. Replacement parts, if needed, can then be purchased from most auto-parts stores.
Open the bonnet and check the brake-fluid reservoir tank. On the Civic, the brake master cylinder is almost always located on the driver's side of the vehicle, bolted to the brake booster. The brake-booster assembly, which is a black metal disk, is bolted to the firewall. The cylinder will have a grey cap on it and a large yellowish, translucent, reservoir tank. The fluid in the tank should be between the upper and lower marks on the side of the tank. If it's not, fill the reservoir with fresh brake fluid.
Pump the brake pedal. If it feels spongy, then there is air in the brake lines and the system needs to be bled by a professional.
Press on the brake pedal. If it sinks to the floor, get out of the car and check under the vehicle. The Civic's brake lines are coated with an anti-corrosion coating, but drivers in the north often experience rusted brake lines on older Honda Civics. A light brown fluid leaking from under the chassis is brake fluid. You'll need to replace the brake lines.
Press the brake pedal. If the pedal is firm, but then slowly sinks to the floor, and there is no evidence of brake fluid leaking, then you have an internal seal failure on your Civic's brake master cylinder. The master cylinder needs to be replaced.
Listen for squealing brakes while driving. Squealing brakes indicates that the wear tab on the brake pads is touching the brake rotors and your brakes need to be changed. Also, vibration or steering wheel "shimmy" during braking indicates uneven brake pad and rotor wear and you'll need to change the brakes under this condition as well.