My brake pedal goes to the floor. Sometimes it will come back up to the normal height and work mint! I changed the master cylinder and bled the brakes and they were mint for a week and all of a sudden they go back down to the floor????

The pads and rotors only have 17k on them so i know that's not the problem....

Wtf? No obvious leaks after a quick look. I already went to A garage for a free check and they wanted $550 to put in the master cylinder and flush the brakes but i spent $60 on the master cylinder and finished in an hour lol.

Any clue?

 

take master back get another

 

I know its not the master cylinder acting up lol

 

Okay quick update.

I adjusted the rear brakes and found a slight improvement but not much. My right rear self adjuster cable is brken back there.

Im going to re-bleed the brakes and put a whole bottle of brake fluid through the thing and see how long it lasts lol.

 

Let me know I have similar problem so i decieded to just swap to discs in rear because maybe the drums were pooped...I shall let you know if that helped....tomarrow? Hopefully it will be done!

 

"they were mint for a week and all of a sudden they go back down to the floor"

That's not adjustment. Did you have the E-Brake partly on all week?

Something really screwy with the rotors/calipers might push pistons back so far you get a bad pedal.

I wouldn't disagree with freedgr! He knows things. I guess if it wasn't bench bled it wouldn't have worked OK for a bit.......

 

It can indeed be the master cylinder. I take it you rebuilt it with a kit?
I've done the same and had to take it out and do it again because a little piece of dirt I did not see the first time is now stuck on one of the rubber cups.

Why did you rebuild/replace it the first time?

 

I bench bled it until there were no bubbles and it was a master cylinder from auto zone. Not an oem master cylinder though.

You were saying a spec of dirt couldve getten back in there and ****ed it up again?

 

You have a leak somewere..... make sure you didn't pinch a line and check your wheel cylinders in the rear

 

Yes quite easily. might have been on the threads of the lines when you put them back in. Doesn't have to a huge chunk to cause a no seal condition and you may not have seen it.

 

i would check for leaks at the wheel cylinders and calipers. It may not be visually leaking at the line connection points but the seals inside these components could be ur problem. I had this same issue after replacing all the faulty components of my power brake system (booster, MC, PV) my system was finally able to function properly showing a leak at the rear wheel cylinder that took about 2 weeks to leak enough that you could see it on backing plate. And like you my pedal felt great at first the slowly faded back to crap. So probably gonna have to get it up on stands and really look at your calipers and wheel cylinders. Then of course bleed the crap out of them lol. JMTS.