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Thread: 2000 WJ soft/sinking brake pedal

  1. #1

    Icon922 2000 WJ soft/sinking brake pedal

    I have a 2000 GC that I have been fighting a soft/sinking brake pedal for some time now. If I push on the pedal when the engine is running, it will go almost to the floor. I have replaced the master cylinder (twice) and bled the brakes multiple times (by pumping and with vacuum pump). I even had Brakes Plus bleed them and cycle the ABS HCU valves (Snap-On tool). The brake pads are new and I do not have a leak (don't have to add brake fluid at all). I would now like to systematically verify the MC is good, then the ABS unit is good, etc. My thought was to be able to disconnect the MC lines and plug the output ports to verify a good MC then do the same to the ABS and work down the system. My question is (finally) has anyone ever done this and where do you get the fittings to block off the ports? They are metric and nobody I went to (NAPA, BAP Geon, etc.) had them. If anyone has any ideas on what else to try or what the problem could be, I am all ears...
    Thanks

  2. #2
    Registered oldgeezer's Avatar
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    My guess is that the brakes work just fine for stopping the moving WJ. When not moving and engine running, the brakes also work by not letting you move on an incline or when you put light pressure on the accelerator pedal. However, when you come to a stop and then press kind of hard on the brake pedal after you have stopped, the pedal moves almost to the floor.

    If all that is what is going on, there is nothing wrong with your brakes. If you press hard on the brakes when the wheels are not turning, the ABS system lets the pressure out.
    2001 WJ Limited, 4.7L, Quadra-Drive -- Kenne Bell Supercharger, Stillen Rotors with MM pads (F/R), Addcos (F/R), Kolak 3 inch exhaust with large case MagnaFlow, Rogue Chrome wheels, DRL activated, and Blaupunkt 3.5" dash speakers.

  3. #3

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    maybe the brake booster needs replacement as well

  4. #4

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    You could have a collapsed soft line. The rubber lines collapse on the inside and at this age your 2000 definitely should have all rubber lines replaced. I did it on my 2000. When they collapse inside they swell and can hold drag on a caliper. I would start with that and then also replace booster and calipers if you can. That is just a start and there may be other problems. Have you considered having a dealership look at it? I would recommend that first.

  5. #5

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    I appreciate your responses. To answer to them:
    -oldgeezer: It does pretty much what you say except when on a trail on an incline, I really felt like the pedal went to the floor and I am not sure it would have held if a rock wasn't behind my tire. Also, I pushed down on the pedal with the engine running on a friend's 2002 WJ and his had a solid pedal not near as far down as mine.
    -It seems like the boost works ok. It does not take a lot of foot pressure to stop.
    -I thought about the collapsed soft line. Wouldn't you be able to see it swell?
    -I have not taken it to the dealer yet. I figured I could replace the bad component for the price they would charge to look at it (but it might come down to that!).
    -Any ideas on block off plugs?

  6. #6

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    how are your rotors? have they been milled down at all?...i would think if the lines swell it would be when you pressure on the pedal...hear is a thought...get some zip ties and put 2 of them about a 1inch apart and snug them up to the rubber lines. have someone press the pedal and hold it down, or even pin a 2x4 on the pedal to your seat or steering wheel to keep pressure on the pedal..then look at the zip ties and see if the rubber hoses swell or become bulbous around the zip ties...

    just a thought....
    99 WJ LIMITED 4.7 230K+ miles.....
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  7. #7
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    Quote Originally Posted by oldgeezer View Post
    My guess is that the brakes work just fine for stopping the moving WJ. When not moving and engine running, the brakes also work by not letting you move on an incline or when you put light pressure on the accelerator pedal. However, when you come to a stop and then press kind of hard on the brake pedal after you have stopped, the pedal moves almost to the floor.

    If all that is what is going on, there is nothing wrong with your brakes. If you press hard on the brakes when the wheels are not turning, the ABS system lets the pressure out.
    I think if you get behind the wheel of most cars and try pushing the brake while sitting still with engine running and in park and you will find the same thing happens. I have had many ask the same question and its normal.
    Old Geeser is correct !

    Good Luck...
    ____________________________________________
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