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need help, problem with brakes

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by cyborg50, Apr 26, 2002.

  1. cyborg50

    cyborg50 Registered Member

    Joined:
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    Location:
    Poland
    hi.
    I own 86 burbon with hydro bost.
    My breaks don't operate well after they going hot.
    It looks like breake pedal don't return to his off position.
    It returns slowly and the brakes operates when i start to drive. If i push the pedal up with my foot the brakes stop braking immediately.
    I suspect hydroboost unit or maybe brake master cylinder.
    What do you think??

    If hydro boost became to have malfunctions, i considering switch to normal vacum operating brakes. (i drive on gas now)
    But i discover that two different power brake unit are:
    w/JB7 and w/JB5. What is the difference? With one is for me? I suspect that if my car is equipt with hydrobost jd5 - jb5 should work fine, if jd7 - jb7 woul be ok. But how to recognize what hydroboost system is instaled in my car??
     
  2. DieselDan

    DieselDan 1/2 ton status

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    My .02, don't scrap the hydraboost; it's a good unit. Yes it sounds like your booster is going bad. Mine started applying (dragging) the brakes this past winter @ 150K. I had access to another used unit so I just swapped out the booster, didn't even have to crack a brake line (Hey it's cold outside!).

    I've heard there is a rebuild kit for the booster build I've never dealt with one. I started to open my old (bad) one up but I could see any obvious failure. I never heard of jd5 or jd7, but I do know there is a difference between K5 (M1009) and K30 (M1008). It's been awhile but I remember to tell the difference look at the accuator shaft. I "think" K30 have a 45' chamfer on the shaft, while K5s have no chamfer or 90' groove/chamfer. (Or this could be backwards).
     
  3. Twiz

    Twiz 1/2 ton status

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    Location:
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    <blockquote><font class="small">In reply to:</font><hr>

    Hi.
    I own 86 suburban with hydro boost.
    My breaks don't operate well after they get hot.
    It looks like the break pedal won't return to it's at-rest position, It returns slowly.
    The brakes operate when I start to drive. If i push the pedal up with my foot the brakes stop braking immediately.
    I suspect hydroboost unit or maybe the brake master cylinder.
    What do you think??

    If hydro boost is the malfunction, I'am considering switching to normal vacum operating brakes. (I have a gas engine, now)
    But I discovered that two different power brake units are avalibe:
    w/JB7 and w/JB5. What is the difference? Which one is for me? I suspect that if my Suburban is equipt with hydrobost jd5 - jb5 should work fine, if jd7 - jb7 woul be ok. But how do I recognize what hydroboost system is installed in my Suburban??

    <hr></blockquote>
     
  4. Twiz

    Twiz 1/2 ton status

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    Location:
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    <blockquote><font class="small">In reply to:</font><hr>

    My breaks don't operate well after they get hot.

    <hr></blockquote>
    This could be normal, Brakes will fade when they get hot, but it would take alot of heat to do that.
    Are the brakes draging? This could cause the brakes to over-heat and fade.

    <blockquote><font class="small">In reply to:</font><hr>

    It looks like the break pedal won't return to it's at-rest position, It returns slowly

    <hr></blockquote>
    Hydro-boost systems tend to have a slow return to at-rest position. All-though, if it is very-slow to return, than you might have a problem. It could be the fluid return circut in the master cylinder, or the booster system. I'm not sure which could be your problem, if that is the case..

    <blockquote><font class="small">In reply to:</font><hr>

    I discovered that two different power brake units are avalibe:
    w/JB7 and w/JB5. What is the difference?

    <hr></blockquote>
    Look inside your glove box, there should be a production label that will have "JB5" or "JB7" onit.
     

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