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Brakes?Which is best to have?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by mudddog91, Mar 6, 2002.

  1. mudddog91

    mudddog91 1/2 ton status

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    Location:
    north carolina
    OK heres the deal,my master cylinder just took a dump the other day and I went to auto zone to get a replacement.I was not sure to get a 3/4 or 1 ton as I have just got the dana 60 up front.When I asked them they asked if the brake system was a JP6 of JP7 or JP8 version,Ive never heard of these numbers before.I know that some 1 tons used hydroboost but I ended up getting a JP7 but I cant seem to get it to get a firm brake pedal.It feels like the fronts are grabbing really good but at about lower than half pedal,and the rears dont seem to be working at all?Anyone got any insight on the master cylinder deal?
     
  2. m j

    m j 1/2 ton status

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    my guess, master cylinder diameter is most liely the JP# differences?
    sounds like you may have gotten a smaller one,if so it would take more pedal travel to displace same volume of fluid.
    but
    when you mention rear brakes seeming ineffective you should look there first.
    there may be a shuttle valve in the combination/proportioning valve that has moved to block the rears.
    it can happen when bleeding.
    is your brake warning light connected? is it lit up when connected?
    are the rear brakes adjusted?
    start with the KISS principle and get the basics covered.
    the master size would not be where i started the troubleshooting
     

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