Long story short(I hope), I replaced a rotted brake line that fed the rear brakes and then also replaced the master cylinder. I bench bled the new MC and had the lines disconnected for about 2 minutes. I have gravity bled the passenger rear and can not eliminate the air bubbles. I’ve read and reread many threads on bleeding and I’m either in denial about air in the ABS or missing something. I reached out to the mechanic who does NYS inspections on my 3 vehicles and he tells me that his shop has similar problems and bleeding is a b@#&ch.
Anyone have better solutions?
Thanks.
Peter S

 

To properly bleed the ABS module in an S10 or Blazer (or really any GM for that matter), you have to plug in a system that can access the body control module and communicate with the ABS module itself. The ABS system has to be engaged and cycled to purge and bleed out the air that gets in the valve, ESPECIALLY if the master cylinder is replaced. I've heard of people getting lucky and getting the system bled the old fashion way, but not very often.

A basic OBDII scanner will not do this. It takes a professional mechanic grade diagnostic computer (or a dealership's equivalent, such as a Tech 2) to access the body control module for this procedure.

It's one of those procedures that takes 5 minutes to do, but requires the right equipment to do so...

 

I was afraid of that. Does activation of the ABS unit provide the necessary pressure to bleed the unit without a pressure bleeder?
I don’t even know what type of ABS system I have.

 

It doesn't provide any pressure, the brake pedal and master cylinder still do that. Basically the procedure is the same as regular brake bleeding, pumping the brakes and then holding pressure on the pedal. Then the system is activated and pulsates the valves in the ABS system, letting fluid flow through them and pushing out the air in the process.

 

So I contacted Autel this AM to see if their Maxi Check Pro could initiate an ABS bleed and “It looks like that your car does not comes with auto bleed function. I'm afraid no scan tools can auto bleed this vehicle.“
I will try the “gravel road stomp” and see how that goes.
Peter S

 

The “gravel road stomp” worked!
After doing a vacuum bleed and gravity bleed on the rears (neither of which completely eliminated bubbles), I had very low pedal. Since I was not driving far to the gravel road I went for it. As soon as I braked the first time the red brake warning light lit up, but there was still braking available. After the first panic stop the warning light went out and I did about six more, never exceeding about 20 mph. The pedal firmed up and was higher than when I began. I re-bled the rears (vacuum and gravity) and the pedal came back to normal. There were bubbles with the vacuum bleed, but none with the gravity bleed the second time.
Hope this helps someone else.
And thanks to all the previous posters.
Peter S

 

Good deal! I have heard of that method being used before, although I've never attempted it personally. But it's basically doing the same thing that hooking the computer up to it does, actuating the ABS valves to purge the system, be it in a slightly less controlled fashion lol.

Glad it worked for you!

 

Thanks for your report and fine write-up.

And Congrats!

 

Incorrect information I think from Autel. Here is the factory information for 1998 Bravada. Clearly indicates to use the scan tool ABS bleed function.

But glad you got yours going.