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brake problem 850

posted by  Blk87 on  Fri May 28 11:27 CST 2010
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last visit: Mon May 27 14:12 CST 2013
[RELATED]

i drive a '95 850. i noticed about 6 months ago or so that sometimes when i hit my brakes, it is either a. very difficult to stop and/or b. a clicking sound is made (sounds like ABS..it goes click click click) along with some resistance from the pedal. at times, this clicking sound turns into a THUNK THUNK THUNK THUNK.
in attempt to find the issue, all four brakes were replaced - calipers, pads, rotors. the problem still persisted. so we disengaged the ABS sensors, thinking that maybe they were bad. it still happened. we even checked out the front and rear ends to make sure nothing was broken.
this is my last resort before i take it to someone, i figured someone has had this problem before. help?? thanks








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    brake problem 850

    posted by  KlausC on  Fri May 28 12:01 CST 2010
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    last visit: Fri Oct 24 10:15 CST 2014
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    There is a check valve in the vacuum line between the engine and booster. A little tough to get off because of the barbs in the valve, but it could be going bad.

    Best booster "test" is to place foot firmly on the brake and then start the engine. The pedal should go down about an inch when vacuum builds. Total failure of the check valve results in no power assist.

    Check any codes in A-3.

    Klaus
    --
    Why are Volvos so endearing? Its just a car.








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      brake problem 850

      posted by  Blk87 on  Sat May 29 06:33 CST 2010
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      last visit: Mon May 27 14:12 CST 2013
      [RELATED]

      hey klaus, did the test and the pedal did not move. valve is bad?








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        brake problem 850

        posted by  Blk87 on  Fri Jun 18 11:29 CST 2010
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        last visit: Mon May 27 14:12 CST 2013
        [RELATED]

        Changed the valve off of the vacuum booster and still no luck. Clicking in the brakes still occurs and there brake pedal does not sink when starting the car when I push it down. What should I try next? :\








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        brake problem 850

        posted by  KlausC on  Sat May 29 06:57 CST 2010
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        last visit: Fri Oct 24 10:15 CST 2014
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        Most likely. Or your engine is not producing any vacuum, which is unlikely.

        Of course, a completely severed vacuum line that leads to the manifold will suck in enough air to nullify the vacuum, but that also leads to other conditions that will produce a check engine condition.

        Verify your ABS codes in A-3. Make sure your ABS light turns on when you turn the key to pos II, before engine start.

        And replace the check valve, not super expensive!

        Klaus
        --
        Why are Volvos so endearing? Its just a car.







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