the brakes on my friends 95 accord sink all the way in once in a while. We thought their was gonna be some air in the lines so we bleed the system. It braked a lot better but the pedal still sinks in and needs to be pumped sometimes but not all the time. what can it be? thanks guys

 

It could be ....
Leak in the brake booster.
Master Cylinder going bad.
Check the Vaccum lines going to the brake brake booster to make sure that all connections are tight, Check the vaccum line for small leaks or cracks.

 

if all your booster lines are good and you aren't having a super hard pedal, the problem could well be the master cylinder bypassing.
Usually it will seep fluid onto the booster directly under where the master mounts up.
An easy test is to check for pedal "creep" ; hold the pedal with steady pressure and it should stay at the same height, if it creeps down the master cylinder is the most likely culprit.

 

all the lines are fine and the pedal does sink so it might be the master cylinder. Is their a better than stock master cylinder that i can use ???

 

I have the same problem but the pedal doesn't always sink.

I had to bleed the brakes a few times because I accidentaly drained the system and introduced air into the lines. I was told that I may have some air still trapped in the master cylinder, is that possible?

Which one usually goes out first, the booster or the master cylinder?

 

Well I know this is late but I'm finaly back from Iraq. The problem was my master cylinder. I just replaced it and everything is cool...

 

lol oddly enough this thread answers my question. had a feeling that's what it was but this confirms it