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Soft Brakes--Update

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by kd7kmp, Aug 15, 2004.

  1. kd7kmp

    kd7kmp Registered Member

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    This is a revisit to a lingering problem I have been having with my 1990 GMC V1500 Suburban. This issue at hand is its brakes--or lack thereof.

    Here is what I have replaced so far:

    Master cylinder
    Front calipers
    Front brake hoses (with rubber replacements)
    Front pads
    Rear shoes
    Combination valve

    The lingering problem is that braking is not adequate. Even at low speeds I can't get the brakes to lock up (this is with the RWAL disabled). I hit the brakes hard going less than 10mph and the truck won't even throw you forward in your seat. The system has been power bled a number of times so I am 110% certain there is no air in it. The rear brakes are working properly and are adjusted properly as well. There is no rear proportioning valve on this truck.

    I have searched through previous posts and have read about replacing the rubber hoses with SS braided lines. I don't feel this will fix the problem alone, hence, I am seeking further knowledge and advice. I appreciate any help you all can give.

    Kevin

    UPDATE:
    I replaced the rear wheel cylinders and the rear brake hose. The truck has a much better feeling brake pedal now. Thanks to all for the help. You guys rock.

    Kevin
     
  2. R72K5

    R72K5 Banned

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    Re: Soft Brakes

    well its good that they arent locking up on you, cuz you dont want that anyways, dunno why you would want that to happen /forums/images/graemlins/confused.gif

    if pedal travel is too far then adjust the rear shoes out more,
    if its not that then bleed air out of system, use hose on bleeder screws put ends of hoses into jar of new fluid, at each wheel in front or rear, pump pedal until no air comes out of hoses,
    then move to front or rear-whichever you didnt do first,

    if pedal slowly sinks at a stop then m/c is junk, or you have fluid leak somewhere

    if it wont bleed right then see if theres a small pin to depress on the combo valve(AKA prop valve)

    depress that while bleeding
     
  3. spearchucker

    spearchucker 1/2 ton status

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    Re: Soft Brakes

    Are the drums and rotors within spec.? Have you tried clamping off the rubber lines to try and isolate the problem? You can make a brake hose clamp out of a couple of smooth pieces of pipe or bolts (don't use threaded part) and a pair of vise grips. Just carefully clamp off the rear hose making sure not to damage it and see if that gives you a firmer pedal. You can also do that to the front hoses.

    BTW: what type of pads/shoes are you using. If you're getting the cheapo ones that are suppose to last a long time then that may be your problem. Get some good quality pads.
     
  4. BAJA_BLAZER

    BAJA_BLAZER 1/2 ton status Author

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    Re: Soft Brakes

    If you really want to figure out your problem, go buy a pressure gauge (2000 Psi) and fittings to test the pressure at each of the four corners. Just hook it up to the bleeder ports and see what reading you get. You should see and hold at least 900 Psi.
     
  5. kd7kmp

    kd7kmp Registered Member

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    Re: Soft Brakes

    R72K5,

    I have a pressure bleeder for bleeding the brakes. And I have always bled with the CV pin depressed. Thanks for the insights. /forums/images/graemlins/waytogo.gif

    Kevin
     
  6. kd7kmp

    kd7kmp Registered Member

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    Re: Soft Brakes

    spearchucker,

    I bought Raybestos pads and shoes. They are both the top grade that Raybestos offers. The rotors and drums were well within minimum/maximum specs. I havn't clamped off the lines, though. I shouldn't need to as the hoses are new and all the metal lines were blown out with brake cleaner. They are all clear. Thanks. /forums/images/graemlins/peace.gif

    Kevin
     
  7. kd7kmp

    kd7kmp Registered Member

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    Re: Soft Brakes

    Using a pressure gauge sounds good. Do you know where I can get one? Thanks. /forums/images/graemlins/thumb.gif

    Kevin
     
  8. kd7kmp

    kd7kmp Registered Member

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    Re: Soft Brakes

    One thing I forgot to add is that the portion of the MC resevoir that feeds the fronts brakes erupts brake fluid like a geyser when I press the brake pedal. I have been told that this is and is not normal, depending on who I ask. Any thoughts? Thanks.

    Kevin
     
  9. BAJA_BLAZER

    BAJA_BLAZER 1/2 ton status Author

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    Re: Soft Brakes

    [ QUOTE ]
    Using a pressure gauge sounds good. Do you know where I can get one? Thanks. /forums/images/graemlins/thumb.gif

    [/ QUOTE ]

    Not in Springville UT /forums/images/graemlins/thinking.gif I used to Deer Hunt just up the canyon from you (Shingle Mill) where the Live Bear Trap is/was. That is beautiful country and some fun wheeling. A good hardware store should have everything you need. I use a gauge to test and set my brake bias on the race trucks and it would be a good way to see if inadequate pressure is your problem.
     
  10. kd7kmp

    kd7kmp Registered Member

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    Re: Soft Brakes

    Thanks for the help. I do love living here. I lived in Rancho Penasquitos for a while with my parents. It's great down there, too.

    Kevin
     
  11. 1-ton

    1-ton 1/2 ton status Premium Member

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    Re: Soft Brakes

    There are two main rules to brake problem diagnosis.

    1. If you can pump your brakes up, then you have air in your lines.

    2. If your brakes do not pump up, but they are still soft, then the rear brakes are your problem.

    I think the problem with your brakes is in the rear. They are either not adjusted tight enough, the wheel cylinders are bad, or the rear brake line needs to be replaced.
     
  12. kd7kmp

    kd7kmp Registered Member

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    Re: Soft Brakes

    1-ton,

    I will look again at the rear brakes. Thanks for the help.

    Kevin
     
  13. spearchucker

    spearchucker 1/2 ton status

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    Re: Soft Brakes

    [ QUOTE ]
    I havn't clamped off the lines, though. I shouldn't need to as the hoses are new and all the metal lines were blown out with brake cleaner. They are all clear. Thanks

    [/ QUOTE ]
    The idea behind the clamp is to cut off the brake fluid to that part of the system to see if the braking improves. For example, you place the clamp of the rubber hose at the rear and make it so the fluid doesn't go to the rear brakes and makes them inoperable. If the braking becomes firmer then you know the problem lies in the rear brakes. /forums/images/graemlins/deal.gif
     

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