2009 brake pedal randomly loses pressure

When I go to stop my pedal will randomly go almost to the floor. No leaks anywhere, master cylinder full. Anybody have this issue ?

 

Brake master cylinder

 

I had that problem with a 2010. Replaced everything - master cylinder, brake booster, pads, rotors, calipers, lines. Had it looked at and bled by 4 different shops. No one knew what the problem was but they all wanted to return it to me and say it was good. I think it was a vacuum leak but traded it before I threw any more money at it.

 

Did anybody ever mention the ABS system. I believe it has valves and seals that can leak and have the same symptoms as a bad master cylinder.

 

My 2011 did this I would stop at a light the all of a sudden start to roll. Changed my master cylinder and fixed the issue. Easy fix just make sure to bleed the master cylinder before installing. Easy as pie.

 

I asked about it a few times. No one would say if they bled the abs. I tried going out and slamming on my brakes a few times to get it to activate and push air through it, but if it was bad I didn’t want to pay over $2000 to replace it.

 

I never had to bleed the abs

 

There is a way to do it but you need techstream to open the valves inside it. Some dealers don’t know and might not do it even when you ask. The alternative is slamming on your brakes and getting the abs to kick in and push out any air.

If he tries everything else and it isn’t fixed, this is worth a shot.

 

Would there be fluid seen.

 

No. It would leak internally.

 

Try your master cylinder mine did the same thing.

I would hold the pedal down at a stop light and it would slowly start to roll. replaced my master cylinder and it stopped my problem. Lived with it a long time with no other issues.

 

Did you fix it yet?

 

My moms car was doing the same I told her it’s probably the master cylinder. A few weeks later she took it to the shop and the master cylinder was leaking.

 

just pump you break a few times, if the paddle hold in the same spot, the master is good, if it sink slowly that's mean the master is leaking. brake booster leak is different, you have paddle pressure, but need a lot of force apply to the brake to stop.