Problems! DOT 3 Synthetic Brake Fluid Yay or Nay?

Discussion in 'KJ General Discussion' started by J33Pfan, Nov 21, 2018.

  1. J33Pfan

    J33Pfan Full Access Member

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    Problems! + DOT 3 Synthetic Brake Fluid Yay or Nay?

    Greetings!

    Having brake problems with my 2002 Liberty 165k miles 4WD V6 ABS. Drums in rear.

    I replaced both front brake lines after Right Front blew out at caliper end. (It was rust rotted where rubber hose meets the metal tube) Calipers work good.

    I was using DOT 3+ brake fluid with no issues. When the brake hose broke, all the fluid left the reservoir, so I had to refill & bleed but I switched to DOT 3 Synthetic.
    I used a compressor powered vacuum bleeder that worked great last flush. I bled brakes per factory instructions. I could actually see the air being bled out.

    After bleeding with reservoir full. The pedal felt great with the engine off.

    After starting the engine I pumped the brakes. ...After a few pumps, the pedal went to the floor and got stuck there. I shut the engine -the pedal eventually back came up. Afterwards the pedal is spongy soft and braking is poor. No Brake Light indicator. (I've never seen this before)

    I dont know how old the Master cylinder is so I'm ready to change it being its age is unknown and pedal hit the floor.

    Questions
    1) Do I need to bench bleed the old master cylinder or is the vacuum bleeding the way to go. Do I need to bench bleed the new master cylinder?

    2) Is DOT 3 Synthetic the problem?

    3) Does this sound like a bad Master Cylinder? ("pedal went to the floor and got stuck")

    Thanks you your input!
     
    Last edited: Nov 21, 2018
  2. cplchris

    cplchris Full Access Member

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    i wouldn't blame the brake fluid for the issue, but a spongy pedal is indicative of air in the system or a leaky seal in the master cylinder. i would try bleeding the brakes again.

    i had a similar experience when i used my motive power bleeder for the first time, I'm not a fan of it because it was a pain to get the cap to seal properly and the fact that it didn't work right the first time, I have always heard people speak highly of the motive bleeder but I wasn't impressed at all.
     
  3. duderz7

    duderz7 Full Access Member

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    Did you also bleed the rear brakes? With the master going dry, I would if you haven't already.
     
  4. J33Pfan

    J33Pfan Full Access Member

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    Yes, everything was bled as per the Manuel. With the vacuum bleeder you can view the bubbles as you bleed.
     
  5. J33Pfan

    J33Pfan Full Access Member

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    Is there a proportional valve that needs to be reset or bled? where is it? or is it a Junction Block? and where is that?
     
    Last edited: Nov 21, 2018
  6. tjkj2002

    tjkj2002 Full Access Member

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    If the master went dry I'd be changing it and having ABS the prop valve is part of the ABS module which needs to be bleed via a scanner that can access that function(your looking at $2000+ scanners for that old).
     
  7. Lancer

    Lancer Full Access Member

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    I had a similar problem after a fluid flush and change. Its either air in the system - especially the ABS, or a seal is leaking or both. I had both, so the seals were replaced and the system properly refilled. As for fluid, I use either a synthetic Dot 4 or 5.1. The fluids are never an issue if they are uncontaminated.
     
  8. J33Pfan

    J33Pfan Full Access Member

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    just noticed this post needed an update to help others with similar ABS MC Brake problems.

    I replaced the MC as the old one was questionable. The new MC came with a reservoir but the Fluid sensor wasnt compatible and I had to use the old reservoir to get the dash BRAKE light to go out.
    The brakes have been working fine with no issues.

    I just Bled the ABS module with my new $120 FOXWELL 630 Scanner. Its all good!