Brake mystery

[Juamgv]

Hey guys!
I bought a 2009 Tahoe Z71 and on my way home realized that needed new brakes. After a month I can't get the truck to brake properly. I will start to numerate what I have done, so you guys can help me to troubleshoot it:
1. Installed new brakes calipers (since 2 had rusted/stuck pistons), thinking it will be the main cause of not braking properly.
2. New brake pads and bleed all old fluid.
3. New hoses (2 front and 4 rear ones) since the fluid was contaminated with small old rubber particles.
4. Pressured air cleaned brake metal lines.
5. New front hubs (came with new abs sensors).
6. All four shocks and coils (for z71).

Everything was good until I turned it on and bleed it, the issue persists... I press the brake and goes all the way down to the floor. At this point no abs light or stabilitrack light on. Next steps:

1. Replaced MC with new one
2. Replaced booster with new one
Issue persists...
Removed EBCM and cleaned it, just in case old fluid clogged it.
Did the bleed again (both, with the scanner and old school way) recovered a little of resistance on the pedal but still takes 3 to 4 pumps to fully stop at low speed.

Lastly... getting back to the garage after testing it the code C0131 popped and both ABS and stabilitrack light are on and seems to stay there forever.

I will appreciate your help!!!

 

[B-train]

Are you sure the system wasn't contaminated with something other than brake fluid? I've witnessed this happen, and did all the repairs. It ruins everything from the MC to the end (calipers/brake cylinders). Everything had to be replaced, ABS and all.

I only ask/mention this because you mentioned small rubber particles in the fluid, and no luck adrer tunnjg throuh the bleeding process. If that's truly the case, you will be replacing everything......again. How did the master cylinder look? Can you see rhe cups - look for swelling and weird fitment/not symmetrical shapes. Same with brake calipers. Basically anything that was in contact with brake fluid and then ANY oil will be F'd and look weird after exposure.

 

[Dustin Jackson]

@Juamgv I'd say you still have air in your lines, it can be hard to bleed it all out. Did you install the new calipers with the bleeder zerk on top? Sometimes people get them on the wrong side making it so they don't bleed properly

 

[Juamgv]

Thank you guys for the info!
@B-TRA everything was removed and new parts installed, the only thing left from original setup are the metal lines, which I cleaned with pressured air from MC all the way back to the rear ones. MC looks good, the piston, the seals and the reservoir, I changed just to be 200% sure it was not it.

@Dustin Jackson you made me check for this one lol. They are with the zerk at the bottom, should they be facing top?

Now I have a question, why with the old components the ABS and stabilitrak light were off?

 

[Fless]

Thank you guys for the info!
@B-TRA everything was removed and new parts installed, the only thing left from original setup are the metal lines, which I cleaned with pressured air from MC all the way back to the rear ones. MC looks good, the piston, the seals and the reservoir, I changed just to be 200% sure it was not it.

@Dustin Jackson you made me check for this one lol. They are with the zerk at the bottom, should they be facing top?

Now I have a question, why with the old components the ABS and stabilitrak light were off?

Tagging @B-train since he wasn't....

They're not zerks, they're bleeders. And they should be oriented up, not down, in order for the air to be pushed out of the lines and calipers when bleeding. Swap those calipers side to side.

 

[donjetman]

you made me check for this one lol. They are with the zerk at the bottom, should they be facing top?

UP

2x what @Fless said

 

[89Suburban]

t-i-t-s up!!!!!

 

[rdezs]

I'm assuming you did a bench bleed on the master cylinder? And used a Tech 2 or similar device to bleed the ABS?

I always pressure bleed the system. Much faster and more effective.

And yeah, the bleeders point up.... If you have them down you have a whole bunch of air in each caliper.

 

[j91z28d1]

@Juamgv I'd say you still have air in your lines, it can be hard to bleed it all out. Did you install the new calipers with the bleeder zerk on top? Sometimes people get them on the wrong side making it so they don't bleed properly

nailed it

 

[Dustin Jackson]

I know this because even with the calipers on the correct side they can be a pain to bleed

 

[Juamgv]

Thank you guys, good catch! T-i-t-s are old... are pointing down. Working on swapping calipers side to side, I will let you know to output in a couple of hours

 

[Charlie207]

Thank you guys, good catch! T-i-t-s are old... are pointing down. Working on swapping calipers side to side, I will let you know to output in a couple of hours

Good luck.

 

[Fless]

The new calipers don't come with new bleeders?

 

[Juamgv]

Latest update: I swapped the calipers from left to right and it did work after a couple of bleeding, brakes are good but not 100% to the point. Now I have a permanent ABS light and Stabilitrak on dashboard, and every other run the BRAKE light. I scanned it and it seems to be the module, the code is C0131.

Any ideas what can it be? I am thinking about a new module but don't want to expend hundreds before making sure it is the module.

 

[j91z28d1]

do you have JL4 rpo code brakes? my software has different diagnostic for with JL4

either way, looks like c0131 should have a sub code of something like 00 or 3A or 4B. for JL4 others like 7 sub codes for different things related to it and how to troubleshoot them.

after checking you have to correct voltage at the correct pins on the harness plugs, with JL4 if 3a or 4b isn't set, you need to do a specal function, Brake Pressure, Sesnor, Calibration..

the hint givin is if they ecu is loosely attached to the hydraulic unit the c0131 can be set and to check for proper torque.

oh and something about make sure the brake lights are working when you press the brake pedal.

 

[Foggy]

You will probably need to cycle the abs pump system as well as part
of the complete bleeding procedure. Need a bi-directional scanner to
cycle it !!!

 

[Dustin Jackson]

@Juamgv It seems like a long shot but maybe you unplugged a wheel speed sensor on accident. I would go reseat all 4 to be sure

 

[dkad260]

If I was trying to solve your issue, I would start with the caliper farthest from the MC, RR, LR, RF, LF in that order.

First, get a bleeder container with soft, flexible hose or similar, these are great from Motive.

Amazon.com

Crack both rear bleeder screws if you have two containers, or just use a hose into a can and let them drip for a few min, or start with the RR.

Close the bleeders then begin the bleeding procedure. Try not to fully depress the brake pedal so it reaches the end of travel....use half presses until it tightens up then you can press the pedal fully. This lessens the risk of damage to the MC piston/seals.

Work all the way around and check the pedal travel. If you pumped a bunch of air you will likely need the ABS bleed procedure from the scanner as previously mentioned.

This works great to get the fluid pushed through the system, just add your models reservoir cap to the purchase.

I don't fill the pressure jug but just add to the reservoir.

 

[Juamgv]

Hey guys thank you for your help! I was out of town and couldn't work on it until yesterday.
@j91z28d1 So the code was the actual brake modulator, it has a switch right in the middle(between all the pistons) with 3 pins, 2 out of the 3 were stuck and didn't make contact with the metal part. I got a modulator from the junk yard and programmed it, all good now!
@dkad thanks, the actual issue with the bleeding process was that the front caliper bleeding valves were pointing down and not up, I swap the calipers and everything came came to normal.
NOW I have a new code C0455 steering angle sensor, I am pretty sure it is not the sensor, could it be because I put new shocks and struts? Do you guys now how to recalibrate it on the tech2?