1990 C1500 ABS (RWAL) removal.

[K15 Blazer]

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in this photo right here, you can see a small 3-way junction block on the frame next to the steering shaft, close to the orange oil filter.... I don't have that.... both my calipers plug directly to the ABS block/pump...

I need to get to the salvage yard and start mocking this up...

 

[someotherguy]

I feel kinda like we're talking in circles. I know it has 4WAL. What I'm saying is generally the 4WAL units used in that era have a separate combo valve that you could simply re-use. Since you're saying yours does not, then go get a combo valve from an 88-94 PICKUP, which is RWAL, and will have a separate combo valve you can plumb in as you eliminate the 4WAL unit. Easy like cheesy.

That pic you posted while I was typing...you are referencing the factory type combination valve I am talking about. It's also the same valve I posted a picture of in one of my other replies to you...

Richard

 

[K15 Blazer]

lol
yeah the combo-valve is the distribution block. which I do have, much like in the above photo.
in OLD gm vehicles you would also have a proportioning valve, but, apparently the "combo-valve/distribution block" is now indeed the pressure proportioning valve.

my concern originally was that my RAWFLFABS-bull unit was the pressure proportioning unit for the whole braking system...

now that I see it is not, I think I can go find that little split block, and plumb my front brakes directly into the "combo-valve/distribution/proportioning block" like this build suggests....

 

[///RAGMC]

I got around to doing this mod on my truck yesterday. I didnt have to use the adapter after all the rear brake line on my truck just screwed into the portioning valve.

 

[NaturalGasForcedAir]

This is for K15 Blazer I just removed my 4 wheel Antilock unit. Its huge, Throw it away.
Then get a 3 way splitter block, (its brass) from a 88-94 pickup.
Then get a proportioning valve from a 88-94 pickup.

Re-route the 2 front lines into the brass splitter block and run one line up to the proportioning valve.
Run the 1 rear line to the proportioning valve.
Bleed brakes and smile!

 

[alanfran]

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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).

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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.

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now we should be looking like this....

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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.

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With all that crap out of the way, its easy to see what we have left to do, which is not much.

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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.

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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.

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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.

OH MY GOD!!! I have brakes! I have Been fighting this thing on and off for three years trying to get it to stop. Replaced EVERYTHING! and all I needed was a $6.00 line fitting? I shall sacrifice cow flesh to the fire gods and dance around the fire naked singing your praises! Wait,, the wife just reminded me that the last time I did that the neighbors didn't talk to us for 3 months. Will you settle for a steak on the grill and me sipping a beer fully clothed? Best I can do.

 

[dfarr67]

I changed the porp valve to a newer rear disk style so needed the conversion adapter- no one had it in my area and I ended up just buying a lot of five off of fleabay. So I four that are left can go- $11 each including shipping in north america. Edelmann 258450 5/16in male into valve, 1/4in female for steel brake line.

 

[DMK1986]

I attempted to do the above; however, in doing so I broke off a fitting in the Proportioning valve. So I had to remove it and drill out the fitting. After doing so I decided to take apart and clean the P-Valve with brake cleaner. After doing so I continued on and finished the above process. During the bleeding process no fluid came out of the rear brakes and while pressing the brake pedal the rotors didn't stop...no rear brakes. I bled the front two just fine. E-brake still work on rear tires, but no real brakes. Crazy thing is my brake pedal is no longer spongy, AT ALL, and I stop light years better...but I now have no rear brakes. Did I kink a steel brake line? Any help would be awesome, thanks!

 

[dfarr67]

There should be a rubber button on one end of the porp valve- press this to recenter valve.

 

[lifted89w/t]

My first time posting after lurking for years.lots of good info here. Ive been trying to get my brakes to work after my 14 bolt swap for a week. Even replacing the rwal unit ( 119$ ) 2 master cylinders,all new calipers brakepads/shoes,rubber lines and drums and rotors. Still having soft brakes. Rip the rwal out throw this fitting on and bamm! I have brakes. Thanks for the write up even tho its a old thread its still good.