Brakes not working properly

Thanks for the information - not quite sure what to do with it. The ABS light is not on.

Well maybe it's not the ABS. All I know is that for example; I needed to pull it out of my driveway onto the street in front of a car this weekend to give it a jump start so in effect I was moving very slow and as I got close to the vehicle and went to stop it wouldn't stop and then I had to jam on the brakes really hard. I'm not sure how else to explain it. There are no visible leaks, reservoir is full, no ABS or Brake Light is on.

I changed out the master cylinder today. Bled it, then bled all brake lines in pattern from back right/left, front right/left. Took it out to drive it and the pedal still feels the same and if I have to stop suddenly the pedal drops to the floor and it almost feels like it surges. No brake lines are open or leaking.

Well, given I am no mechanic thus having a scan tool that step was not completed.

Would have been nice to sort this out but that is not going to be the case absent taking it to the dealership.

I see there is a plethora of scan tools listed on Amazon but I'd have no clue which cheap option would allow for this procedure.

I know absent doing this there is still air in the line. I was using the bottle method with the bottle 1/3 full connected via a tube to the bleeder and I would gently pump the pedal about 5-10 times, at least to see the fluid color shift and then would move onto the next caliper.

Well I bought scan tool - Foxwell NT630 and proceeded to bleed the brakes again.

The scan tool really didn't have a workflow that stepped through each brake line. Rather it would basically say to get it ready, I would open the bleeder which is connected to a hose into a bottle with brake fluid, I would get back into the vehicle and it would say to press and hold the brake - the ABS then would cycle several times and the workflow in the scan tool would end. Without lifting up on the brake pedal I would keep it held down with a DIY bar. I would go close the bleeder and then proceed to the next line set.

After all said and done, I cannot feel a difference - still plenty of pedal movement and spongy.

Not sure where to go next on this.

Okay, so herein is my lack of experience.

Are you saying that what I should have done is the bleeding through all four wheels; back right, left, front right, left?

After that part then do the automated bleed with the bleeders closed?

I just presumed that was the entire point of the exercise was that the ABS pump would auto bleed and to do so I needed to have the bleeder open at the time the scan tool told me to push and hold the brake pedal, then repeat for each wheel.

May I ask why the automated before the manual bleed?

One last question. Is it fair to say that some vehicles, not this suburban year, would have a scan tool work flow that is guided through each wheel? I ask because I have watched a few YouTube videos and see where the scan tool work flow directs the user to each wheel but in my case I only have one option in the scan tool and the workflow is just to hold the brake pedal until it cycles and the workflow ends. Or is this more so related to the type of scan tool, meaning mine is a cheap version compared to professional grade scan tool?

Roy, I ended up having the GM dealership take a look at it and they said they had to bench bleed, and then do the scan tool, manual bleed, yada, yada. They just returned to me. Brakes feel the same. I back into my driveway and they had pulled it in so when I went to turn around the vehicle to pull forward and I was barely moving and put on the brakes it did the same thing, didn't want to stop and the pedal surged quite a bit.

On a side note: I primarily had it there because I noticed a power steering leak and while they inspected they found a coolant leak on the down side hose from the overflow. Curious to know if you can comment if this cost is in the ballpark of average or did I get overcharged? Power Steering High Pressure Hose $129.95 and the Coolant Hose was $122.95 and all told with labor it was $566.53.

I am going to retire this vehicle to anyone who will give me a few bucks for it.

It was good vehicle for me for the past 8 years. Time to move on to a newer vehicle. Different problems : )

Roy, still driving it. My purchase of a new vehicle is on hold.

So I want to continue to troubleshoot this brake problem.

Could it possibly be the brake booster?

As far as repairs for the brake system. Last winter had a brake line burst in the back by the axle per the GM dealer which they fixed. I replaced both rear calipers. Lastly the master cylinder recently.

When driving it again today the pedal surges at the end of the stroke as the vehicle is coming to a stop. When it surges like this it allows the vehicle to move more forward than originally intended if that makes any sense.