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2004 Chevorlet Suburban Brake Pedal to Floor

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by TechAnalyst, Nov 14, 2010.

  1. TechAnalyst

    TechAnalyst New Member

    There are a lot of posts on this however I've done almost everything listed before posting.

    1.) New Brakes
    2.) New Rotors
    3.) New Master Cylinder
    4.) Brakes Bleeding Perfectly

    I still have brakes but they dont work until it nearly hits the floor, now I was thinking a power booster but everything I read the symptoms seem more like air in the system, but on the lines theres no air.

    Possible that its air in the abs?
    Last edited: Nov 14, 2010
  2. stephan

    stephan Rockstar 4 Years 5000 Posts

    Welcome to the GM truck club Tech
    Like you say it could be air in the lines, but you also say the brakes were bled perfectly. Is this one of the systems that require the fancy GM dealership bleeder to do it properly?
    Either way, I would check the adjustment of the rear brakes. You may be using all your pedal stroke just to get them to make first contact.
    Don't really know what your original problem was so it's hard to go from here.
    I agree it's probably not the booster itself, but the adjustment on the master rod could be excessive.
    When the pedal finally takes up the slack, is it hard or mushy?
    With or without the engine running, is it the same?
  3. TechAnalyst

    TechAnalyst New Member

    The original problem was the Brakes would work but holding on the pedal it would slowly decline towards the floor, again still had breaks, now this problem I have read is common with a master cylinder or air in the lines and it only started shortly after new rotors and new pads.

    I was stupid and let the truck sit to long and the batt died so Im charging it and once I drop it back in and give it a run Im hoping things will be back to normal.

    Im thinking your on the right track, it might be a system where I need the Tech II tool because of the ABS System, but if it was the ABS in the way would I still get perfectly bleeding brakes?
  4. stephan

    stephan Rockstar 4 Years 5000 Posts

    If you hold pressure on the pedal & start the engine & the pedal goes down some more, this is ok as it indicates the booster is working.
    However the rod could still need adjusting if the master wasn't a genuine GM replacement. There have been issues with aftermarket master cylinders having a longer distance from the M.C mounting point on the booster, to the inside depth in the piston where the rod engages it. If you still have the original m.c. measure it & compare to the new one. If the new one is deeper set, then you will need to lengthen the rod by the same amount.
    I have read on other forums that sometimes the brakes bleed fine by the owner & there are no problems, & sometimes they require the GM tech bleeder. It's kind of a crap shoot. Did you bench bleed the master before you installed it? If not, then you would have circulated all that air through the system & some may still be in there even though you are getting solid fluid out when you bleed it. If that's the case you will need the "General" to bleed it.
  5. TechAnalyst

    TechAnalyst New Member

    Did the bench bleed

    I probably need the "General" to do something :p I wanted to avoid their massively over priced rates, $90 an hour and everytime Ive gone to them theyve made issues worse. I had zero issues with my brakes, after they installed new rotors and brakes Im left with the issue I have now, and I paid them over $1500 for more problems.
  6. stephan

    stephan Rockstar 4 Years 5000 Posts

    Do you still have the old M.C. so you can measure like I told you above?
    If not, then before you take it to the dealer for bleeding, try slowly pushing the pedal down with your hand & see if you can feel or hear the booster rod clicking as it takes up slack between the rod & the back of the master piston. If you can then you will need to adjust the rod longer.

    Have you checked the rear brake adjustment?
  7. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Yea with this yr model and ABS you need to use the GM tool, your bleeding results will appear to work properly but you'll still could still have air in the lines, the GM tool helps bleed the ABS and brake Bias valve.
  8. stephan

    stephan Rockstar 4 Years 5000 Posts

    Hey Tim, what is the tech 2 bleeder all about anyway. Are they just reverse bleeding the system, or is it something else? Also,what year did the GMs start requireing this t-2 bleeding??
  9. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    I'm not a 100% sure everything the T-2 bleeder does, I know it opens the bias valve all the way, as far as the ABS I'm not sure what it does to that while bleeding.
    My understanding is it overrides the speed sensors and opens the wheel cylinder valves to allow them to flow, I always thought you could do this by removing the ABS sensor but a GM tech told me doing it this way you miss a step that allows the lines to still hold air, the wheel cylinder valves dont open all the way when the sensors dont record any speed.
    Depending on the truck they started using it as far back as 96 on 1500's, around 97 it started showing up on 2500's.
    I've bled the brakes on my previous 98 without the t-2 tool (by pulling the ABS fuse) but I never got that solid feeling, the next owner took it to a GM garage and said they got quite a few bubbles out of the lines, so I know it does make a difference.
  10. stephan

    stephan Rockstar 4 Years 5000 Posts

    That's some good stuff Tim, thanks..:great:

    This part you said here could easily be it---> the wheel cylinder valves dont open all the way when the sensors dont record any speed.

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