The brake system of all modern cars is a hydraulic system. It uses a pump, called a master cylinder, to create pressure. That pressure pushes smaller cylinders, which press the pads against a spinning metal disc or drum to stop the vehicle. When this system gets air in it, the pedal will feel soft or it doesn't engage the brakes quickly. You can make the brake pedal more sensitive by bleeding the air from the brake system. Not only will this fix your problem, but it is also good maintenance for your brake system.
Open the bonnet and locate the master cylinder reservoir -- the white plastic container near the rear driver's side of the engine compartment. Remove the lid from the master cylinder reservoir and fill the reservoir with DOT 3 brake fluid.
Raise the front or rear of the vehicle with a floor jack and place jack stands below a secure part of the vehicle. Lower the vehicle until its weight rests only on the jack stands.
Fill the empty container with about 3 inches of new DOT 3 brake fluid.
Crawl beneath the vehicle and locate the brake bleeder valve -- the 1/4-inch metal valve at the top of the caliper. Place the rubber hose on the bleeder valve.
Place the free end of the hose into the container of DOT 3 brake fluid. Make certain the end of the hose remains submerged in the fluid.
Instruct an assistant to press and release the brake pedal until it feels firm, then hold pressure on the pedal. Loosen the brake bleeder valve, as your assistant holds the pedal. Observe as bubbles come from the end of the hose in the brake fluid. Tighten the bleeder valve.
Repeat Step 6 until no bubbles come from the hose.
Repeat Steps 2 through 7 on the remaining three wheels.
Raise the vehicle from the jack stands, using the floor jack, and remove the stands from under the vehicle. Lower the vehicle to the ground.
Check the fluid level in the master cylinder reservoir: It must be between the "Min" and "Max" lines. Add DOT 3 fluid as needed. Close the master cylinder reservoir and the vehicle's hood.
If your vehicle has drum brakes, the process is identical, only the brake bleeder valve is located in the top-rear of the brake backing plate. Take the old brake fluid to your local parts store for proper disposal.