spongy brakes

on my 2001, the brake pedal is spongy, and makes a faint groaning sound when you press down. I am guessing that the likely cause is air in the lines or a master cylinder problem. I have changed brake pads, but have never learned to bleed the lines. What is involved?

you can gravity bleed if no helper is available.fill master cyl. & leave cap off
open bleeder & let it bleed out 1 or 2 bleeders at a time.
keep an eye on brake fluid so you dont run dry

Thanks. I was at the parts store and found a little "One Man Brake Bleeder Kit". Looks like it will work fine. Contains a good set of directions, and plays right into what I already know about the process. Will post back as to how well it works.

I bled the brake lines. Had air in right rear and right front. Just a little. Everything is working like brand new now! The little "one man brake bleeding kit" from the parts store worked great. Total job took about 30 minutes for all four.