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Help with 1990 K1500 Braking System (RWAL)

This is a discussion on Help with 1990 K1500 Braking System (RWAL) within the Technical / Maintenance forums, part of the General Discussion category; Hello All, 1990 K 1500 with braking issues. Pedal goes to floor, long stopping distance but I will stop. I ...

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    Help with 1990 K1500 Braking System (RWAL)


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    Hello All, 1990 K 1500 with braking issues. Pedal goes to floor, long stopping distance but I will stop. I replaced Master, front calipers, rear cylinders, new pads and shoes. Bench bled master cyl. Bled at all fours wheels (RR, LR, RF, LF). I do have vacuum going to the brake booster. The truck has the RWAL anti lock brake system. The module and isolation/dump valve cluster next to the master cylinder. I believe either air is in this RWAL system and I do not know how to bleed it and in what order. OR I believe the RWAL system is faulty due to time, moisture, mixing dot3 and 4, or whatever. So what are my options after bleeding the RWAL system (post instructions please). I was thinking about pulling the whole mess out (bypass it all together). Would that be possible, legal, or just crazy. Let me know please, any help would be greatly appreciated.

    Brian-

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    Re: Help with 1990 K1500 Braking System (RWAL)

    Have you searched? Common to bypass the rwal. I did it to mine and it helped the pedal and braking force a lot. Pretty simple just needed one adapter from the parts store.
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    Registered User burt's Avatar
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    Re: Help with 1990 K1500 Braking System (RWAL)

    Lots of people have bypassed it. I almost did but got it the air out of it by getting it to cycle a bunch. I went out in a snowy field and slammed on the brakes getting the wheels to lock up several times.

    1993 K1500 4.3 V6 4x4

    We've idiot proofed the world... now its full of idiots.

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    Registered User bowtie44s's Avatar
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    Re: Help with 1990 K1500 Braking System (RWAL)

    I'm going through the same thing. I had a code 10 brake light. You can unplug the black box and the light will go out. I slammed the brake and the rear wheels locked, I definately need to do something to cut force to the back. I know I can run an adjustable wilwood proportioning valve if I have to. What did you do mxhalofan?
    Jeff

    '88 chevy k3500 aluminum head 454
    NV 4500

    '84 chevy short bed dana 60 14bolt ff 383 stroker
    44" boggers (rear) 44" tsl (front) hydraulic assist
    welded front and rear 5.13 gears
    th400 np205 twin stick -SOLD-

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    Re: Help with 1990 K1500 Braking System (RWAL)

    Quote Originally Posted by snbi View Post
    Hello All, 1990 K 1500 with braking issues. Pedal goes to floor, long stopping distance but I will stop. I replaced Master, front calipers, rear cylinders, new pads and shoes. Bench bled master cyl. Bled at all fours wheels (RR, LR, RF, LF). I do have vacuum going to the brake booster. The truck has the RWAL anti lock brake system. The module and isolation/dump valve cluster next to the master cylinder. I believe either air is in this RWAL system and I do not know how to bleed it and in what order. OR I believe the RWAL system is faulty due to time, moisture, mixing dot3 and 4, or whatever. So what are my options after bleeding the RWAL system (post instructions please). I was thinking about pulling the whole mess out (bypass it all together). Would that be possible, legal, or just crazy. Let me know please, any help would be greatly appreciated.

    Brian-
    Thanks guys for your response. I dont know why its so hard to find instructions to bleep/purge that thing. Seems like I can find everything but that. I am so tempted to bypass the whole thing. I ll keep looking for a few more days. But any more ideas are appreciated.
    Thanks again, Brian-

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    Re: Help with 1990 K1500 Braking System (RWAL)

    Brian, I have a 90 k1500 and to get good brakes on my truck I installed a master cylinder for a 2002 k1500 Suburban and 1990 k2500 8600gvw calipers. I also removed the abs modulator but do that at your own risk. You'll need a blf-19c brass adapter if you decide to go with this master cylinder.
    Last edited by LackytN; 02-20-2013 at 05:43 PM.

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    Registered User 92k1500chevy's Avatar
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    Re: Help with 1990 K1500 Braking System (RWAL)

    I didn't need the adapter to bypass the RWAL on my 92 so if you end up needing it let me know and I'll see if I can find for you and it's yours. Definitely consider doing it, the brakes on my truck are now the best they've ever been.

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    Re: Help with 1990 K1500 Braking System (RWAL)

    Quote Originally Posted by 92k1500chevy View Post
    I didn't need the adapter to bypass the RWAL on my 92 so if you end up needing it let me know and I'll see if I can find for you and it's yours. Definitely consider doing it, the brakes on my truck are now the best they've ever been.
    How did you bypass it? I was wanting to run right to the mc and use an after market prop valve for the rear. Are you using the stock prop valve?
    Jeff

    '88 chevy k3500 aluminum head 454
    NV 4500

    '84 chevy short bed dana 60 14bolt ff 383 stroker
    44" boggers (rear) 44" tsl (front) hydraulic assist
    welded front and rear 5.13 gears
    th400 np205 twin stick -SOLD-

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    Re: Help with 1990 K1500 Braking System (RWAL)

    Quote Originally Posted by bowtie44s View Post
    How did you bypass it? I was wanting to run right to the mc and use an after market prop valve for the rear. Are you using the stock prop valve?
    Just use the factory proportioning valve, the simplest way is to find a coupling and connect the two lines that went to the rwal valve together

    1993 K1500 4.3 V6 4x4

    We've idiot proofed the world... now its full of idiots.

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    Re: Help with 1990 K1500 Braking System (RWAL)

    Quote Originally Posted by burt View Post
    Just use the factory proportioning valve, the simplest way is to find a coupling and connect the two lines that went to the rwal valve together
    I'll give that a try, I unplugged the wires but when i slam the brakes it just locks the rears.
    Jeff

    '88 chevy k3500 aluminum head 454
    NV 4500

    '84 chevy short bed dana 60 14bolt ff 383 stroker
    44" boggers (rear) 44" tsl (front) hydraulic assist
    welded front and rear 5.13 gears
    th400 np205 twin stick -SOLD-

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    Re: Help with 1990 K1500 Braking System (RWAL)

    Quote Originally Posted by burt View Post
    Just use the factory proportioning valve, the simplest way is to find a coupling and connect the two lines that went to the rwal valve together
    I'm not sure what you're saying. I'm sorry to thread jack but i'm sure he's looking for the same information. Here is what I have.

    It is hard to tell from the pic but coming from the back of the mc,is a 3/16 line that goes into the front of the proportioning valve (I assume the aluminum peice is the proportioning valve.) Coming out of the front of the prop valve is a 3/16 line that goes to the front wheels. Coming from the front of the mc and going to the back of the prop valve is a 1/4 line. Now what is that rusty piece with the bleeder on the top of it? I'll call it the brake booster but correct me with the right name. Coming out the back of the prop valve, there is 5/16 line that makes a loop and goes to the back of the "booster" A 1/4" line goes from the front of the booster to the rear wheels. Which 2 do I couple together? Here is a quick sketch I made to help clear it up.

    Jeff

    '88 chevy k3500 aluminum head 454
    NV 4500

    '84 chevy short bed dana 60 14bolt ff 383 stroker
    44" boggers (rear) 44" tsl (front) hydraulic assist
    welded front and rear 5.13 gears
    th400 np205 twin stick -SOLD-

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    Re: Help with 1990 K1500 Braking System (RWAL)

    bump
    Jeff

    '88 chevy k3500 aluminum head 454
    NV 4500

    '84 chevy short bed dana 60 14bolt ff 383 stroker
    44" boggers (rear) 44" tsl (front) hydraulic assist
    welded front and rear 5.13 gears
    th400 np205 twin stick -SOLD-

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    Re: Help with 1990 K1500 Braking System (RWAL)

    This is what i was going to do, but your RWAL module thing looks a little different than mine.

    That rusty piece in your picture is your RWAL module. The two lines that go to it need to be coupled. It would be alot easier to just screw the line form the rear brakes right into the proportioning valve but i think they are different sizes or something.

    1993 K1500 4.3 V6 4x4

    We've idiot proofed the world... now its full of idiots.

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    Re: Help with 1990 K1500 Braking System (RWAL)

    Quote Originally Posted by burt View Post
    That rusty piece in your picture is your RWAL module. The two lines that go to it need to be coupled. It would be alot easier to just screw the line form the rear brakes right into the proportioning valve but i think they are different sizes or something.
    Yes, one is 5/16 and one is 1/4. Now that I know what needs done, I'll see what I can do. If not I'll just run them to the mc and use an aftermarket proportioning valve. Maybe mines different because it's an 88 or because it's a 1 ton I don't know. Do I need to cap off the module, remove it, or just leave it open? the wire from the control box goes to the center of the prop valve which was making me wonder if it was the control module but I guess not.
    Jeff

    '88 chevy k3500 aluminum head 454
    NV 4500

    '84 chevy short bed dana 60 14bolt ff 383 stroker
    44" boggers (rear) 44" tsl (front) hydraulic assist
    welded front and rear 5.13 gears
    th400 np205 twin stick -SOLD-

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    Registered User burt's Avatar
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    Re: Help with 1990 K1500 Braking System (RWAL)

    Quote Originally Posted by bowtie44s View Post
    Yes, one is 5/16 and one is 1/4. Now that I know what needs done, I'll see what I can do. If not I'll just run them to the mc and use an aftermarket proportioning valve. Maybe mines different because it's an 88 or because it's a 1 ton I don't know. Do I need to cap off the module, remove it, or just leave it open? the wire from the control box goes to the center of the prop valve which was making me wonder if it was the control module but I guess not.
    You can remove the RWAL module and the black box if you want. The wire that goes to the proportioning valve is just a sensor I think.

    I did a little research, looks like the older trucks used your style of RWAL unit and the newer trucks went to an aluminum one.

    1993 K1500 4.3 V6 4x4

    We've idiot proofed the world... now its full of idiots.

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    Re: Help with 1990 K1500 Braking System (RWAL)

    the brown wire goes to the brake pressure switch.
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    Re: Help with 1990 K1500 Braking System (RWAL)

    Thanks Burt. I think this will work. http://www.coleparmer.com/buy/produc...-31412-54.html Should be able to join the 5/16 to the 1/4.
    Jeff

    '88 chevy k3500 aluminum head 454
    NV 4500

    '84 chevy short bed dana 60 14bolt ff 383 stroker
    44" boggers (rear) 44" tsl (front) hydraulic assist
    welded front and rear 5.13 gears
    th400 np205 twin stick -SOLD-

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    Re: Help with 1990 K1500 Braking System (RWAL)

    I actually did this today on my 89 1/2 ton.. I just ran the rear 1/4 inch line from the rear brakes into a 7/16-28 iff to a 1/2-20 iff adapter and screwed it into the bottom of the prop valve and bled the system.. piece of cake..

    I personally would NEVER use a compression fitting to ever join brake lines together...
    1989 K1500. Caddy 500, 14 Bolt 3.42 gears, NV4500, Axle Flip Rear, 2500 keys up front..
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    Re: Help with 1990 K1500 Braking System (RWAL)

    kzhurley is right, NEVER use compression fittings on brake line. If you are set on bypassing, go for it. The RWAL system is crap. Personally, I would just try unplugging it and bleeding the RWAL system by cracking the lines loose at the master then after the ABS unit. They will usually bleed there, with the RWAL unplugged it probably won't ingest air again and your problem may be solved. Again, a clean bypass would work with probably equal amount of work.

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    Re: Help with 1990 K1500 Braking System (RWAL)

    I have used a lot of compression fittings over the years and never had one problem. The lines always rust before the compression fittings fail. What do you guys have against them? What is an iff fitting and where do you get them? I already ordered the 5/16 x 1/4 compression fitting but if that looks better i'll get them. Yes, the rwal is terrible. I am surprised gm never got sued or recalled them.
    Jeff

    '88 chevy k3500 aluminum head 454
    NV 4500

    '84 chevy short bed dana 60 14bolt ff 383 stroker
    44" boggers (rear) 44" tsl (front) hydraulic assist
    welded front and rear 5.13 gears
    th400 np205 twin stick -SOLD-

 

 
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