Originally Posted by red94teg
I was driving today and I noticed that at a stop if I kept my foot on the brake with some resistance, it would slowly sink down toward the floor. It would never actually hit the floor completely but this is definitely a new problem nonetheless. What could be causing this issue? Is my master cylinder on the way out, or could it be something else?
Sounds like either the master cyl or brake booster (or the check valve on the brake booster). Never had to buy either for a Honda, but for other cars you can get a master cyl/booster combo for not too much.
Most times it's the master cyl. The fluid under pressure leaks past the seals to the unpressurized side and back to the resevior. Since the leak is internal you won't see a loss of fluid or any wet spots. I bring up the booster since I've seen them do some really funky stuff.
FWIW, I've seen the sinking pedal problem go on for years and just be an annoyance, YMMV.