Another ABS question

[Alaskaburb]

You'll also need two or three of the GM J-39177 "special tools" (or aftermarket/home-made equivalent) for holding the valves open

So I was able to bleed the system yesterday as much as I could with the avaliable fluid on hand. I was able to use a short strip of wood and to clamps to loosely replicate the J-39177 tool. I opened the valve on the ABS module as outlined in the instructions and I had clean bubble free fluid on all 4 corners. My ABS light and brake light are both still on and testing braking on a gravel road in both forward and reverse I only have front brakes. I have the JD7 brakes if that matters.

 

[Schurkey]

So I was able to bleed the system yesterday

What method did you use to bleed the brakes?

Did you use a scan tool? Did the valves chatter?

I had clean bubble free fluid on all 4 corners.

So you have a free-flowing fluid path all 'round.

My ABS light and brake light are both still on

What ABS codes? The "BRAKE" light is not because of the Safety Switch or the park-brake pedal switch...right?

and testing braking on a gravel road in both forward and reverse I only have front brakes. I have the JD7 brakes if that matters.

No ABS chattering when stopping?

Are the rear brakes in proper adjustment?

 

[Alaskaburb]

What method did you use to bleed the brakes?

I used the two person method to bleed the brakes but I only had one bottle to refill with. Fluid would flow clean and bubble free at all 4 corners.

I do not have the code reader yet. It has been stuck in Kent Washington for the last three days.

As far as proper adjustment they are new in the rear and installed by a shop. The E brake works as it should and I did several aggressive reverse stops to self adjust. At some point I will need to take them apart but I have decent confidence in the shop that did the work.

There is no ABS chattering at all. Until the ABS light came on I would hear the ABS unit cycle at 10mph ever since I bought it. It has stopped cycling.

Next on the agenda is to replace the master cylinder and then bypass the ABS if the code readerdoes not help with diagnostics.

Thanks again!!

 

[Schurkey]

I do not have the code reader yet. It has been stuck in Kent Washington for the last three days.

You need a scan tool, not a code-reader.

I thought you had access to a Solus Pro, just waiting on the Loaner scan tool so you can use the adapter.

There is no ABS chattering at all. Until the ABS light came on I would hear the ABS unit cycle at 10mph ever since I bought it. It has stopped cycling.

An obvious change in operation surely indicates a problem.

Next on the agenda is to replace the master cylinder and then bypass the ABS if the code readerdoes not help with diagnostics.

Why are you replacing the master cylinder? You've already determined that the Safety Switch isn't triggering the instrument cluster BRAKE light, so the hydraulic system doesn't seem to be unhappy.

Again, a code-reader is not a suitable tool. Better than nothing, but not efficient or complete. HOPEFULLY the Solus Pro has software suitable for your ABS auto-bleed, but even if it won't auto-bleed, you should be able to get readings on the speed sensors.

 

[Alaskaburb]

Again, a code-reader is not a suitable tool. Better than nothing, but not efficient or complete. HOPEFULLY the Solus Pro has software suitable for your ABS auto-bleed, but even if it won't auto-bleed, you should be able to get readings on the speed sensors.

So the community scan tool arrived but for some reason will not communicate with my Suburban. Good news though the adapter is working with the new Snap-ON Solus tool I have here. Here is the weird part. My car has 4 wheel ABS but the scanner I have here will only work if I tell it I have rear wheel antilock. It will run the test, I hear the ABS module activate and then I get every every possible code related to the ABS module. I am going to watch the Snap-on tutorial and connect the scanner to WiFi and try again.

** update** I was able to the the Edge scanner to read. The ABS motor cycled and the list of codes is long. The first code is "failed ECU." My assumption is the rest of the codes are related to the because of the failed ECU.

 

[Schurkey]

Yeah, yeah, CODES.

What about getting DATA; including from the wheel speed sensors? Do you have the option for Auto-Bleed?

What software versions are on those scan tools?

 

[Alaskaburb]

Update
My ABS module and related components are now located in the landfill and my suburban stops smooth and the rears will lock after the fronts when I step on the pedal hard. I do not have an ABS light obviously and the “Brake” light works only when the parking brake is applied. Here is what I did from memory. ** if you have working ABS or resources to repair yours I would not remove it** 1993 K2500 8600 GVW JD7

1.) Unplug electrical connectors on the ABS module.

2.) Disconnect and remove all lines connected to the ABS module with exception to the two fronts and one rear line going to their respective brakes. These three remained connected to their respective locations.

3.) Remove 4 bolts holding ABS module in place and smile when depositing unit in garbage can.

4.) Remove factory combination valve and replace it with the following unit. ** may not be necessary** I was able to just loosen the lines at the master cylinder and then disconnect from the combination valve. Do not remove the lines from the master cylinder rather rotate them up above the fluid level and then retighten to contain the fluid. You do not want to bench bleed the master if you can help it so don't let all the fluid drain out.
https://www.summitracing.com/parts/CLP-PVKS-B1

5.) Remove switch from original combination valve and clean with brake cleaner. Apply super glue to grounding pin where it enters the plastic housing. Allow to dry upside down with pin facing up.

6.) Position the original brake lines where they need to be for the new combination valve by bending them carefully and cutting to length. Once roughly in place remove the line from the vehicle for flaring. I did not have to do any crazy bending of the lines and the original retainer clips worked fine. Carefully find the right fitting for the line size that matches your new combination valve as the originals on the truck were the wrong size. Make sure to slide the new fitting over the line with the correct orientation and flare the line. I was not about to fiddle around with the old clam shell flaring tools so I went all in with the following tool and it worked great!
https://www.eastwood.com/professional-brake-tubing-flaring-tool.html

7.) Connect lines one at a time and tighten firmly with the correct flare nut wrench.

8.) Fabricate and flare lines from the master cylinder to the combination valve. Install in the correct orientation. The rear of my master cylinder went to the front port of my combination valve. **verify yours**

9.) Remove the warning light switch from your new combination valve and **TEMPORARILY** replace it with your old cleaned and super glued switch. I did not have access to one of the little plastic or aluminum combination valve bleeding tools at the time. There is debate here on the forum if it is needed or not but I was remote and did not want any problems. Here is the tool I replicated. **I think**

Classic Performance PV-TOOL Classic Performance Combination Brake Proportioning Valve Tools | Summit Racing

Free Shipping - Classic Performance Combination Brake Proportioning Valve Tools with qualifying orders of $109. Shop Brake Proportioning Valve Tools at Summit Racing.

www.summitracing.com

10.) Thoroughly bleed and flush the system in the proper sequence. RR, LR, RF and LF. I used the Motive products pressure bleeder with the correct adapter.
https://www.summitracing.com/parts/mvp-0250

11.) Clean all brake fluid from connections with brake clean and allow it to dry. inspect for leaks at every new connection.

12.) Gradually increase pressure at the brake pedal and inspect for leaks and tighten and clean as needed.

13.) If you have done everything correctly and there were no existing problems with other components you are ready for a road test. I stepped on my pedal hard to make sure everything held before I ever took it out of park. While I had nothing to run into should the system fail, I had blocks prepositioned just a few feed ahead as a backup. My burb is out in the sticks on gravel so I had plenty space and no traffic to deal with. The gravel also made it easy for me to gradually increase my stopping effort to see when wheels locked up.

14. inspect for leaks after the road test and over the next few days

** my suburban lives out at our cabin in Alaska so I rarely do any high speed driving or winter driving. if this were not the case I may have put more effort into getting the system repaired.

I am sure I left something out so please let me know and I can edit this over time. I hope this helps!