Help with brakes before I pull my hair out

[cofferson]

TLDR: I was having brakes sticking issues. After replacing everything I can't get a firm pedal. Wondering if ABS valve failure is common.

I own a 2008 Suburban 2500. The brakes were dragging so I started going around all four corners replacing pads and rotors. I also replaced the rear calipers (fronts are newer) and and guide pins and caliper brackets as necessary. Greased everything up and bled the brakes easy enough. Went for a drive and all felt fine but quickly turned sour. Brakes started dragging and then after hitting the brakes particularly hard, they stayed fully engaged. I punched the brake pedal, heard a light pop and the brakes released. At this point I changed the soft lines thinking MAYBE those were bad. They were perfect all the way through. I then figured that since it sat for a long while, it may be that the master cylinder piston is sticking. Replaced both the master cylinder AND the hydrobooster because the hydrobooster was leaking. Thankfully I did this because they were seized together and still are. I bench bled the master successfully and put the new parts on and went to bleed the brakes. Never really got any air out. Now I have an extremely soft pedal. Pull the lines back off and air got back in the master. Bench bled it again and put on vehicle with plugs and got a very firm pedal. Put the lines on and this time I didn't use a vacuum bleeder incase I somehow sucked in air, still a very soft pedal. So now I used a scan tool to bleed the ABS and still never got air out. At this point I'm at a loss because brakes are very simply. I feel like I'm chasing a ghost and at this point the only thing I can think is the ABS module has something wrong with it and once I replaced the master cylinder I basically screwed myself. Truthfully I don't know exactly how the valving works to understand the root cause myself so I'm wondering if anyone here has thoughts on if this could be the abs unit? It may even be that the ABS is what was causing issues all along and now it's either not allowing air through due to valves sticking or it's bypassing the pressure.

Thanks guys. I really want to get this on the road and it's making me highly regret even buying it even if that's an irrational thought..

 

[justchecking]

Have you checked again to make sure you have the new calipers on the correct sides?

 

[cofferson]

Have you checked again to make sure you have the new calipers on the correct sides?

Yes

 

[justchecking]

Man. On my 2011 I accidentally let all the brake fluid drain out while I was running to the auto parts store to get parts. I was able to bleed end to end with no problem. Are you pushing the pedal all the way to the floor or only 3/4 of the way? Should only be 3/4. Other than that I don’t know. Good luck!

 

[Rocket Man]

I highly recommend the Motive power bleeder especially in cases like this. It uses pressure instead of vacuum so there’s no way to introduce air into the system unless you let it run dry. It also makes it super easy for one person to bled the entire system. Also you don’t need a compressor running to create a vacuum like the ones that (literally) suck. Make sure you get the one for late model GM vehicles.

 

[Charlie207]

I only have a 1500 chassis, but whenever I do brake work it takes a couple days for the pedal firmness to fully return. This includes not even cracking any brake lines/draining fluid, but just compressing the calipers to make it easier to remove and reinstall after doing other suspension stuff.

Try parking on a steep uphill slant for a few days to let all the potential air bubbles gravity bleed.

 

[cofferson]

Man. On my 2011 I accidentally let all the brake fluid drain out while I was running to the auto parts store to get parts. I was able to bleed end to end with no problem. Are you pushing the pedal all the way to the floor or only 3/4 of the way? Should only be 3/4. Other than that I don’t know. Good luck!

Thanks. This kind of affirms that something is wrong. I've replaced master cylinders and have redone entire brake systems many of times but never on ABS vehicles. I have this unfortunate hunch that the abs valving is leaking internally causing either trapped air or bypassing the pressure. Because I've done everything I can think of and it's a very soft pedal.

 

[cofferson]

I highly recommend the Motive power bleeder especially in cases like this. It uses pressure instead of vacuum so there’s no way to introduce air into the system unless you let it run dry. It also makes it super easy for one person to bled the entire system. Also you don’t need a compressor running to create a vacuum like the ones that (literally) suck. Make sure you get the one for late model GM vehicles.

Thanks. I used a pressure bleeder as well to no avail.

 

[Fless]

Check out Eric O's procedure and tips.

 

[swathdiver]

TLDR: I was having brakes sticking issues. After replacing everything I can't get a firm pedal. Wondering if ABS valve failure is common.

If the ABS module or pump was no good, you'd get codes for it.

Did you follow this exactly? How many quarts of fluid did you go through? I use 4 to 6 each time.