1990 C1500 ABS (RWAL) removal.

Discussion in 'Lowered and Bagged Suspension' started by hefftone, Jun 9, 2012.

  1. hefftone

    hefftone I'm Awesome

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    This is easy to do, but with a little information it will make it easier and more straight forward. My truck is a 1990....it seems that this should be the same on c1500's from 1988* to 1994*.
    What you need.
    1/2" wrench/socket
    9/16" and 1/2" flare wrench for brake lines.
    5/16" male x 1/4" female brake line adapter fitting. ie, EDELMANN #258450 (available at O'reilly auto parts.....about $5.)
    15 minutes + time to bleed your rear brakes.


    The Master cylinder has the fluid reservoir on top. The isolation dump valve is below it (to be removed). To the right of that is the proportioning valve (gotta keep that). Attached to the proportioning valve is the control box (black plastic with wired connectors).
    2012-06-09120715b.jpg



    Lets Start off by removing the control box. First, remove the connectors from the rear. The top one is part of the vehicle harness. The lower plug connects to the other part that will be removed. Then, jiggle the box and pull towards the front of vehicle. Should slip off.

    2012-06-09120722.jpg

    now we should be looking like this....
    2012-06-09120731.jpg

    Next, disconnect the two lines from the bottom of the isolation/dump valve...one of the lines is very short and connects to the proportioning valve. Disconnect from the proportioning valve as well. After those are removed, simply remove the two bolts (1/2" socket/wrench) from the the top of the valve where it attaches to the bracket.
    2012-06-09120801.jpg

    With all that crap out of the way, its easy to see what we have left to do, which is not much.
    2012-06-09120849.jpg
    2012-06-09120854.jpg

    I bought this fitting at Oreilly auto parts for $5.49 plus tax. It will allow you to use the existing brake line and screw into the proportioning valve. It is EDELMANN 258450. The male threads are 5/16" and the female are 1/4". This is a brake fitting. You can probably find something similar but those are the right dimensions.
    2012-06-09120508.jpg

    Screw that in the bottom of the proportioning valve. I used some teflon tape for good measure. The use a little bending to reposition the line and tighten it up.
    2012-06-09121347.jpg

    And that's it! Bleed your Rear brakes, hopefully you have will better pedal feel. Mine have improved greatly, but still feels a little spongey for my liking.
     
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  2. DRAGGIN95

    DRAGGIN95 Warranty Killer! Staff Member

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    Nice job! Rep for you!
     
  3. 93SierraWT

    93SierraWT Greater Made Chevy

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    What are the benefits of doing this?
     
  4. hefftone

    hefftone I'm Awesome

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    The isolation/dump valve is thought to degrade the brake pedal feel and and trap air. And besides, the system only provides anti-lock braking for the rear wheels, via the drum brakes. Probably not the.most effective design. My brake light was on and the truck had no stopping power. I did this after bleeding all four wheels. Its much improved now.

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  5. dropped93

    dropped93 I want one of everything

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    I have the same problem, will be doing this soon, thanks for the write up.


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  6. Swims350

    Swims350 I'm Awesome

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    did the same thing on my 88 a few weeks ago, haven't bled them yet but mine had a blf-19c adapter and it was 1/2 to 7/16 pretty sure. I got it from autozone looks the same as yours, amazon has them and so does advance.

    100_4164.jpg
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    100_4165.jpg
     
  7. DRAGGIN95

    DRAGGIN95 Warranty Killer! Staff Member

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    Yes this help's you have a much firmer brake pedal, and help's the truck stop faster, the original abs design on these was no good!
     
  8. Swims350

    Swims350 I'm Awesome

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    wow thanks for the confidence boost man. I'm looking forward to that for sure.

    I got brand new brakes all around and it still sucked, new pads, shoes, calipers and wheel cylinders. Now I got new flex lines and did this mod, can't wait to bleed em and test em.
     
  9. Pierced

    Pierced Allen AKA BargainJoe

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    By deleting this will it throw an abs code/light?
     
  10. dropped93

    dropped93 I want one of everything

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    I can't speak for the 94+ but on the 88-94 it gets rid of the brake light


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