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  1. #11


    check your brake booster is it vacuum or hydro? There was a recall on the 04 hydro boosters. If it is hydro, look under your dash where the rod goes from the pedal thru the fire wall. Is it leaking there?
    Last edited by Pikey; 10-20-2012 at 10:01 PM.

    1995 Silverado 4x4
    6" BDS Suspension Lift-3" Body Lift-Add A Leaf in rear -Trailmaster SSV Shocks-Duel Steering Stabilizer Kit -AirAid Cold air intake-
    4.56 Gears with Detroit Auburn Locker-Pro-Comp Traction Bars with duel shocks-Aluminum Skid Plate Kit-38.5" x 16.5" Mickey Thompson Baja Claws-Constant Dropping fuel gauge

    2005 Yukon XL Jet Power Programmer, Bilstein Shocks, Bilstein rear springs, Helwig Anti-sway bars, EGR Window Visors, EGR Hood Shield, Denali Headlights, Headlight harness upgrade, GE NightHawk Bulbs, White Night Rear lighting system, Russell Braided SS brake lines, PowerStop Brake pads, PowerStop cross drilled and Slotted Rotors,
    2002 Silverado ext cab 2wd (Sold)
    2003 Yukon XL (Totaled)

  2. #12


    No, still having the same problem. Dealer and mechanics do not know what it is. I think it may be in the PCM. But, there are no codes either. I might consider replacing it. I`m to the point of giving up on it.

    Pikey, I have replaced everything that is brake related on this thing. Nothing fixed it. The only thing that has not been replaced are the front brake lines.

    2004 Chevrolet Silverado 1500; 4x4; Ext. Cab; 5.3L FI

  3. #13



    Though not as common as vacuum booster power brake systems, some vehicles are equipped with Bendix "Hydro-Boost" power brakes. This system uses hydraulic pressure generated by the power steering pump rather than engine vacuum to provide power assist.
    Pressure generated by the power steering pump is stored in an accumulator, which is then routed to the master cylinder by the Hydro-Boost unit when you step on the brakes. Problems can be caused by leaks inside the Hydro-Boost unit, by a worn power steering pump, slipping or broken pump drive belt, or hose connections.
    A simple way to test the Hydro-Boost system is to pump the brakes five or six times with the engine off to discharge the accumulator. Then press down hard on the pedal (about 40 lbs. of force) and start the engine. Like a vacuum booster, you should feel the pedal fall slightly when the engine starts, then rise.
    The leakdown of the accumulator can be checked by pumping the brakes several times while the engine is running, then shutting it off. Let the car sit for about an hour, then try the brakes without starting the engine. You should get 2 or 3 soft brake applications before it takes more effort to push the pedal.

  4. #14


    I have same problom on my 2004 4x4 took to midas yesterday and they bleed entire system including master cylinder with ther snapon scan tool. Working great so far

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