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Thread: NEED hydroboost brakes

  1. #1
    Join Date
    May 2012
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    55

    NEED hydroboost brakes

    i have a 91 s.c. and the hydroboost brakes are faling. the pump in it runs continuously and killed my car. it doesnt build up pressure for brakes to work. so im assuming im going to need the entire booster. so if anyone knows where i can get one or has one that would be great. if it must be delivered id like to do paypal or c.o.d. this way no one gets messed over. thanks guys. Devin.

  2. #2
    Join Date
    Oct 2004
    Location
    Charlotte, NC
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    Several things can cause the pump motor to run all the time....

    Most likely the pressure switch not cutting power to the pump....

    Are you getting and dash lights (red brake and amber ABS lights).....

    What do you mean when you say it "killed your car"....

  3. #3
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    May 2012
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    It killed the battery because it was just running and running all day. The accumulator was hot as well.

  4. #4
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    May 2012
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    I don't think the brake light is on bit the yellow ABS is definitely on.

  5. #5
    Join Date
    Jul 2003
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    Eastern (nee Western) PA
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    If it ran all day, even with the key turned off, then I think the ABS relay is stuck and needs to be replaced.
    God bless!!!

    1990 SC auto ... red outside, gray cloth inside ... ~205,000 miles (and climbing) ... driven daily!

  6. #6
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    Quote Originally Posted by S_Mazza View Post
    If it ran all day, even with the key turned off, then I think the ABS relay is stuck and needs to be replaced.
    I would check the brown ABS relay first as it is the easiest part to get to.....

    Pull it out and apply voltage to the two small terminals.....

    If it is good, you will hear and feel it click....

    You said the accumulator was hot.....

    Do you have enough brake fluid in the reservoir....

    Your accumulator could be bad....

  7. #7
    Join Date
    Apr 2002
    Location
    Lakeville, MN
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    For the ABS pump to run all the time, and with the key out, it is likely the pressure switch has failed, and the power relay for the brakes has failed. The high temperature of the fluid will be from the high heat generated from the pump running all the time.

    A good resource for the braking system on your car is at the 35th Anniversary site.http://www.35thatr.org/Tips/ABS.htm has a description of how to trouble shoot the system with wiring diagrams and testing ideas.

  8. #8
    Join Date
    May 2012
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    55
    Awesome info guys thank you, this is frustrating to say the least. Also. Where would the brown? ABS relay be located at?

  9. #9
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    May 2012
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    Ok so according to this website the accumulator is bad. When reassembling the system I checked the little hose to make sure it was free of anything. But for it Eton run when the key is off? And for so long to kill the battery? It should have "overheated" and shut off. There is plenty of fluid in it

  10. #10
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    Eastern (nee Western) PA
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    Quote Originally Posted by Moshman1205 View Post
    Ok so according to this website the accumulator is bad. When reassembling the system I checked the little hose to make sure it was free of anything. But for it Eton run when the key is off? And for so long to kill the battery? It should have "overheated" and shut off. There is plenty of fluid in it
    I think you may be quoting the website out of context. I mean, maybe the accumulator is bad. But the pump should never run when the key is off. You have to check the control side of the system.

    I am not sure if you can unplug the pressure switch connector to isolate the relay part of the system and test for the fault there. Maybe Big E knows. But the relay is not that hard to get to anyway. It's on the firewall, near the passenger side shock tower. The only thing you might need to remove to get it out is the BAP sensor, which just has 2 screws, and the cowl weatherstrip.
    God bless!!!

    1990 SC auto ... red outside, gray cloth inside ... ~205,000 miles (and climbing) ... driven daily!

  11. #11
    Join Date
    Oct 2004
    Location
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    The brown ABS relay is located on the firewall, under the windshield cowling, near the passenger side hood strut....

    It can be a pain to get to as it is tucked in there pretty good.....

    You might have better luck removing the holder that it sits in to get better access to it.....

    Once you have it out, do like I said in my previous post to test it....

    If it turns out to be bad, you can still get them at the parts store or I have quite a few of them.....

  12. #12
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    May 2012
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    I am unsure. But ill check it when I charge the battery.. what would make the accumulator go bad exactly?

  13. #13
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    May 2012
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    And the entire wiper assembly is out of the car so everything is decently simple to get to now

  14. #14
    Join Date
    Apr 2002
    Location
    Lakeville, MN
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    You should start a thread in the tech forum.

    From this statement
    the pump in it runs continuously and killed my car.
    It seems you have more problems than possibly a bad accumulator. The accumulator is just a steel container with an elastic wall inside. One side of the elastic wall is charged (or should be charged) with nitrogen gas. The other side is the hydraulic fluid in your system. when the pump runs it pushes hydraulic fluid against the divider which compresses the nitrogen gas. This continues until the pressure limit of the system is reached, sensed by the pressure switch. The compressed gas stores the pressure and is supposed to release it back into the braking system when you step on the brakes in the form of assist.

    If the Accumulator is bad, the nitrogen charge has escaped into the brake fluid and then out into the atmosphere. The accumulator is no longer able to store any pressure, and fills up with brake fluid. This leads to the pump having to run more often than it otherwise should.

    This does not lead to the ABS pump running all the time, even with the key off. That is a different problem.

  15. #15
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    May 2012
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    Ahhh gotcha.. and a couple people on here gave me some things to check, but this method of brakes is frustrating to say the least. I'm ready to throw in the towel and convert it to the crown Vic brakes or whatever. This is my daily, or supposed to be, and at 66xxx miles the entire brakes fail lol.. but anyway, what should I check for the continuous running issue do you think? What the other person said before in this post?

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