Something is terribly wrong with my brakes. Every so often, when I step on the pedal, it just keeps going into the floor without slowing my car much at all. I need to pump it a couple times for it to begin working. Then the next time I use it, it works fine. It used to happen every two weeks or so, but it is becoming more frequent. It happened twice today. My mechanic just replaced the rear brakes and refilled the brake fluid a few days ago, but this was happening long before I took it in. What could the problem be?

 

leak in your lines probably? is your brake fluid resivoir getting lower and lower?
Could be air in lines too but your mechanic should have bleed them properly I would hope

 

sounds like signs of a master cylinder going bad

 

The brake lines need to be bled.

 

I agree with both, get a buddy to help you bleed your brakes. If that doesn't solve it, next is the master cylinder. Replace it and it should be fixed.

 

With my exp. with hondas, I can almost guarantee you it's the master cylinder. No little leaks in the lines will cause that much of a drop in your pedal. Go to advance auto parts, pay $68 and put it in, or take it to a place and pay $100+ or so and they will put it in and re-bleed your lines, and you're set. I just did a brake master cylinder on my accord last week. Works perfect now

 

100% sure it's the MC. If there was a leak, he wouldn't be able to pump it up. It would just lose more fluid with every push. Anyway, see if you can find someone who knows how to bench bleed your new MC before you install it. Makes things 10x easier

 

air in lines can do the same thing, if the air bubbles just move around in system and then occasionally come back to MC.

 

yeah it was the master cylinder, thanks guys.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mattsnooz &raquo;</TD></TR><TR><TD CLASS="quote">air in lines can do the same thing, if the air bubbles just move around in system and then occasionally come back to MC.</TD></TR></TABLE>

Air doesn't just get into the brake lines on its own. Only from improper bleeding or some kind of leak