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Suburban brake problem. 1987 w/ 454

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by Davidh, Mar 19, 2013.

  1. Davidh

    Davidh New Member

    I posted earlier but put in the wrong spot. I have 87 suburban with 454. The rear brakes are not working. I went to bleed them and am not getting any fluid from the rear brakes. The pedal is spongy and goes almost to the floor. I am getting fluid to the rear proportioning valve that is attached to the . But the wheel cylinders are dry. I s there another valve somewhere. Is there a way to test the from proportioning valve?
  2. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    Disconnect the rear side of the valve, have someone push the pedal, no fluid equals bad valve.
  3. Davidh

    Davidh New Member

    Took the wheel cylinder off the right rear and pumped the brakes. Got a good stream out of the brake line. got new wheel cylinder and will put it on. Is there a way that the cylinder could be clogged and not bleed.
  4. Davidh

    Davidh New Member

    suburban brake problem

    Took off wheel cylinder and got a good stream from the brake line when brakes pumped. Will replace the wheel cylinder . can the wheel cylinder get clogged and not bleed?
  5. Davidh

    Davidh New Member

    Disconnected the rear side of the proportion valve get a weak stream of fluid. With the rear wheel cylinder off I get a stream but it is not strong. petal is mushy. brake light is on I have replaced the master Cylinder and bleed the front brakes. get a little fluid form the rear when bleeding. I used the cap from the new MC and blocked off rear line of the MC and got a full pedal. Here is my question can the proportion valve be bad and let a little pressure out but not enough to activate the brakes or is it one of those parts that either works or does not?
  6. Davidh

    Davidh New Member

    Have put on a 2nd master cylinder. The first one was leaking. A right rear wheel cylinder. Getting a little fluid out of the new wheel cylinder. disconnected the rear line to the proportioning valve and got a little bit of flow. I am pulling the proportioning valve. and replacing it as I expect it is partially plugged. I am thinking of putting a used one one as I cannot find anyone in my area who can get a new one.
    Last edited: Mar 22, 2013
  7. Davidh

    Davidh New Member

    Have now put on two master cylinders. The first one was leaking. Replaced the rear wheel cylinders and the proportioning valve. Again tried to bleed them and get just a trick out of the right rear wheel and nothing form the left rear wheel. Uncoupled the rear line form the proportioning valve and get fluid but not a strong stream. Should I be getting a lot of fluid out of the proportioning valve. it seems like no pressure. Do these valve need to be reset? I checked all the lines and not kinks or breaks in the lines.
  8. vncj96

    vncj96 Epic Member 5+ Years 1000 Posts

    with something that old it mught be wise to just do a full break line replacement, could be filled with gunk or debris
  9. Davidh

    Davidh New Member

    Is changing the lines pretty complicated? I was considering disconnecting the line and blowing them out.
  10. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    The lines are steel, they will rust and corrode. New lines would be the best answer if they are that plugged. A hard stop would probably blow one of the lines.

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