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  • Help with 1990 K1500 Braking System (RWAL)

    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-

  • #2
    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.
    89' K2500 SLE 350/700R4 ECLB 270K 4:10 gears Dual Efans
    Rebuilt tranny, all new AC parts. 95 mirrors, 6.5's in the doors.
    Soon: 94' instrument cluster and power window/locks

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    • #3
      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.

      Comment


      • #4
        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 roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap

        Comment


        • #5
          Re: Help with 1990 K1500 Braking System (RWAL)

          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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          • #6
            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, 05:43 PM.

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            • #7
              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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              • #8
                Re: Help with 1990 K1500 Braking System (RWAL)

                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 roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap

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                • #9
                  Re: Help with 1990 K1500 Braking System (RWAL)

                  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.

                  Comment


                  • #10
                    Re: Help with 1990 K1500 Braking System (RWAL)

                    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 roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap

                    Comment


                    • #11
                      Re: Help with 1990 K1500 Braking System (RWAL)

                      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 roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap

                      Comment


                      • #12
                        Re: Help with 1990 K1500 Braking System (RWAL)

                        bump
                        Jeff

                        '88 Chevy K3500, aluminum head roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap

                        Comment


                        • #13
                          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.

                          Comment


                          • #14
                            Re: Help with 1990 K1500 Braking System (RWAL)

                            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 roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap

                            Comment


                            • #15
                              Re: Help with 1990 K1500 Braking System (RWAL)

                              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.

                              Comment

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