Last night I installed stainless steel brake lines and replaced the rotors and pads on my 2000 Maxima. I replaced all of the old fluid with new super blue and bled out all of the air. The problem is that I can't maintain a firm pedal. I can pump up to get a firm pedal but if I release pressure on the pedal and wait a minute when I press on the pedal again it goes all the way to the floor.

I was thinking I might have a bad master cylinder but I didn't have this problem when I started so I am drawing a blank.

Any help would be appreciated.

Thanks in advance
Chris

 

You've still got air in the system. It can take a lot of bleeding to get all the air out of the system sometimes. Try starting the engine to intitialize the ABS system, shutdown the engine, and rebleed. Repeat that a few times and see if that helps. You may have "emptied" the reservoir and got air in the whole system including the ABS module which can make it harder to get the air out of the system.

 

When you say you "replaced all the old fluid with new super blue", how exactly did you do that? Did you suction out the old fluid from the brake fluid resevoir, fill to top with super blue and then bleed each brake line, farthest to closest, until blue fluid came out, making sure that the reservoir never ran dry?

If the reservoir ever ran dry, as P.Samson said, you likely still have air in your system. Also, when pumping your brake pedal to bleed the system, be careful not to push the pedal down much past where you normally could push the pedal during a hard stop. It could mess up the seals in the master cylinder...

 

another tip:

before bleeding the system, after you turn off the car and disconnect the battery, pump the pedal several times until it gets really hard - this gets any excess air out of the brake booster/ABS system.

I forgot to do this on my last bleed and had the same problem as you. Then I re-did it correctly and problem solved.

 

Thanks for the info. Hopefully it is just an air bubble and not a bad seal on the master cylinder. I will keep you posted

 

Is it necessary to disconnect the battery while bleeding the brakes?



Anyhow, after you bleed the brakes w/ new fluid, should the pedal feel different, firmer? I suppose if you change the fluid every year or two, it shouldn't make a difference. But I just changed the original stuff out of mine, low mileage car, but w/ brake fluid it doesn't make a difference of mileage. Anyhow, the pedal feels the same or very minimal difference if at all, after the fluid change. I made sure all the fluid being pumped out had no air bubbles, then I had my wife step on the brake a few more times to make sure, it was just a stream of blue with no bubbles. I didn't disconnect the battery and I didn't do farthest to closest, would it make that much of a different?

 

Update: The pedal feel is slightly firmer on the road, not quite as noticeable idling. However, my pedal was never mushy to begin with.

 

thats good to know, gotta try it next time.

 

After you've finished bleeding, start up the engine, press down on the brake pedal like you would to stop the car, keep your foot on the pedal, shut off the engine continue keeping your foot on the pedal for 15-20 secs. If the pedal doesn't travel any, then you shouldn't have any air in the system.