Help with brakes before I pull my hair out

[rdezs]

.... And if you have it, it's worth pulling the fuse and see if the symptoms change.

 

[rdezs]

Just had a few minutes and did some basic research. Dragging brakes are pretty common issue when there's a defect in the traction control system, which your vehicle should have. The number one culprit is the system is detecting wheel slipage incorrectly. Often this is due to a bad wheel speed sensor for the reluctor ring that it gets the signal from. Rather than just throwing parts at it, you need a scanner to look at life data while you drive and see what each speed sensor is showing. Your ECM is what interprets the signals and since the message to apply or release brakes. You will not necessarily get a warning light if the ECM thinks it is getting correct data..... I'm not sure if any aftermarket my directional scanners have the capabilities you need for this. Definitely worth a try to disconnect the battery for 15 or 20 minutes, then touch both cables together to release any stored power in capacitors..... And reconnect.

In the absence of having a Tech 2, it might be easier for you to let the dealer have it for 1 hour. That's their minimum charge, usually around $180. It should only take them about 20 minutes.... Plus if there's an update available for your ECM they will do that.

 

[petethepug]

Got some damn good data in this thread.

Food for thought is the compression fittings in the system too. I had a sitch on a clutch slave circuit that would always catch air after a day.

The flange on a steel hardline had cracked where it compressed over a fitting. Vibration was the culprit. Going with a braided stainless hose stopped the vibration from carrying through the line and destroying itself.

 

[cofferson]

Just a quick update:

Over the weekend I received a replacement master cylinder and an ABS valve block. ABS valve block is put to the side but on hand in case I need it, can be returned for full refund.

I bench bled the master cylinder perfectly until no compression (realistically just a teeny tiny bit but that's normal) and put it on the truck. Then I pressure bled and again never got any air bubbles but a soft pedal. As one last hail mary before putting the ABS block on I decided to switch things up. Had my wife come out and instead of pump, hold, open bleeder, close bleeder, release I decided to do what you shouldn't do and I instructed her that we would open bleeder, stomp brake pedal hard and fast, close bleeder, release. The problem is this will disperse the air into smaller bubbles BUT.... we started doing this and every hard press I could literally hear the air banging through the lines. Finally I got foamy air out of one rear line and one front line. Didn't get anymore air so I did the ABS autobleed and the sound was drastically different and the pedal actually would modulate. Still not a firm pedal but I am letting the air bubbles resettle overnight and through today and we will try again later tonight. I am hopeful since that was the first air we even got through. Again, I've never had this much issue getting some damn air out rebuilding brake systems before, but I've only ever done this on older vehicles without ABS.

 

[Rocket Man]

Just a quick update:

Over the weekend I received a replacement master cylinder and an ABS valve block. ABS valve block is put to the side but on hand in case I need it, can be returned for full refund.

I bench bled the master cylinder perfectly until no compression (realistically just a teeny tiny bit but that's normal) and put it on the truck. Then I pressure bled and again never got any air bubbles but a soft pedal. As one last hail mary before putting the ABS block on I decided to switch things up. Had my wife come out and instead of pump, hold, open bleeder, close bleeder, release I decided to do what you shouldn't do and I instructed her that we would open bleeder, stomp brake pedal hard and fast, close bleeder, release. The problem is this will disperse the air into smaller bubbles BUT.... we started doing this and every hard press I could literally hear the air banging through the lines. Finally I got foamy air out of one rear line and one front line. Didn't get anymore air so I did the ABS autobleed and the sound was drastically different and the pedal actually would modulate. Still not a firm pedal but I am letting the air bubbles resettle overnight and through today and we will try again later tonight. I am hopeful since that was the first air we even got through. Again, I've never had this much issue getting some damn air out rebuilding brake systems before, but I've only ever done this on older vehicles without ABS.

By pressure bled, please explain. What device have you been using to pressure bleed? Pressure bleeding does not require moving the brake pedal. that is manual bleeding. Pressure bleeding involves using a tank attached to the reservoir. The tank holds extra brake fluid and is then pumped up by hand similar to a garden sprayer so there is pressure forcing the fluid into the system, then you simply go to each bleeder valve and open it up and let fluid flow out until all the bubbles are gone, then move to the next. The extra fluid in the pressure bleeder automatically fills the reservoir as you go. Maybe I’m misunderstanding what your process has been to bleed the system.

 

[Skywagon]

any time I bleed brakes on any vehicle, car, truck, motorcycle.....these get installed first. I even installed them on my abs unit on my motorcycle. It makes it stupid easy. No affiliation.

https://www.speedbleeder.com/

 

[cofferson]

By pressure bled, please explain. What device have you been using to pressure bleed? Pressure bleeding does not require moving the brake pedal. that is manual bleeding. Pressure bleeding involves using a tank attached to the reservoir. The tank holds extra brake fluid and is then pumped up by hand similar to a garden sprayer so there is pressure forcing the fluid into the system, then you simply go to each bleeder valve and open it up and let fluid flow out until all the bubbles are gone, then move to the next. The extra fluid in the pressure bleeder automatically fills the reservoir as you go. Maybe I’m misunderstanding what your process has been to bleed the system.

What I meant was that I was pressure bleeding getting no air through so I went back to a revised manual bleed to get some air through finally.

 

[07Cadillac]

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..

You may need a scan tool to bleed abs. module. Had to do on 2007 escalade

 

[Rocket Man]

What I meant was that I was pressure bleeding getting no air through so I went back to a revised manual bleed to get some air through finally.

So what device are you using for a pressure bleeder? I find it impossible to get absolutely no air out if you replaced the master and used a pressure bleeder. Also, last time I did the entire system using the Motive, I used over a gallon of fluid.

 

[cofferson]

So what device are you using for a pressure bleeder? I find it impossible to get absolutely no air out if you replaced the master and used a pressure bleeder. Also, last time I did the entire system using the Motive, I used over a gallon of fluid.

Basically the same as you but Orion bleeder. just your typically pump up pressure bleeder. I'd think it was impossible too but here we are.

 

[cofferson]

You may need a scan tool to bleed abs. module. Had to do on 2007 escalade

Yes, I am using a scan tool to do the autobleed sequence.

 

[j91z28d1]

Just a quick update:

Over the weekend I received a replacement master cylinder and an ABS valve block. ABS valve block is put to the side but on hand in case I need it, can be returned for full refund.

I bench bled the master cylinder perfectly until no compression (realistically just a teeny tiny bit but that's normal) and put it on the truck.

I'm curious about this? I've bench bleed tons of master cylinders. but this doesn't sound familiar? what do you mean by no compression? the internal piston should he compressed completely till it bottoms out. the last little bit of air in that front res is always the hardest to get to.

 

[cofferson]

I'm curious about this? I've bench bleed tons of master cylinders. but this doesn't sound familiar? what do you mean by no compression? the internal piston should he compressed completely till it bottoms out. the last little bit of air in that front res is always the hardest to get to.

Of course. What I mean is I prefer to use a kit with hoses so I can be sure no more air is circulating. I prefer this over the "plug ports and pump until air stops rising into reservoir" method since it never works for me. BUT, when I am done, I remove the hoses and install the provided plugs for installation so I don't have to worry about dripping. Once they are installed I can now also check for any compression which should be none. Basically, bleed master cylinder, plug off ports, now piston can no longer move. If air is still trapped and the plugs are installed, I would be able to compress the piston still. Kind of a clunky explanation sorry..

 

[NardDog]

Consider the caliper pistons could be getting stuck and either rebuild them or get new ones. Edit looks like you might have replaced them already.

 

[j91z28d1]

Of course. What I mean is I prefer to use a kit with hoses so I can be sure no more air is circulating. I prefer this over the "plug ports and pump until air stops rising into reservoir" method since it never works for me. BUT, when I am done, I remove the hoses and install the provided plugs for installation so I don't have to worry about dripping. Once they are installed I can now also check for any compression which should be none. Basically, bleed master cylinder, plug off ports, now piston can no longer move. If air is still trapped and the plugs are installed, I would be able to compress the piston still. Kind of a clunky explanation sorry..

ahh. that makes more sense. I've never capped off a master after bleeding. I just turn them side ways so they don't drip.


and we bleed brakes at work by pumping up the pedal till hard, hold and open so it sprays out hard. sometimes you might have to start the equipment to get a good stream. you might try that. give up on the power bleeder and go old school haha. we don't even have one at the shop. I do have one at home but only because this hybrid's braking system has a specific TSB about bleeding brakes because dealer techs couldn't do it. you need something crazy like 25psi on top of the master to bleed correctly. that would damage a normal plastic master.

 

[cofferson]

ahh. that makes more sense. I've never capped off a master after bleeding. I just turn them side ways so they don't drip.


and we bleed brakes at work by pumping up the pedal till hard, hold and open so it sprays out hard. sometimes you might have to start the equipment to get a good stream. you might try that. give up on the power bleeder and go old school haha. we don't even have one at the shop. I do have one at home but only because this hybrid's braking system has a specific TSB about bleeding brakes because dealer techs couldn't do it. you need something crazy like 25psi on top of the master to bleed correctly. that would damage a normal plastic master.

Well I couldn't get any more air so I went for a drive and the brakes were fine BUT my initial problem of the brakes staying engaged after hard was still present. To be fair almost everything needed replaced anyway because the car sat with my father in law for 2-3 years with brake fluid that was blackish green.

Anyway, I isolated the dragging to the rear right which was toast when I picked it up from dragging. Took it for a test drive with the scan tool and saw that if I brake heavy enough to make the inlet valve in the ABS module activate, the brake will remain engaged until I pump the pedal. If I brake heavy but just under ABS activation. It doesn't stick. So the ABS valve block is probably all corroded and gunked up from sitting and was also what was probably causing my bleeding issue.

 

[cofferson]

While we're here. Anyone got a trick for these rusty flare nuts? Idk why GM decided the ABS module should be here this close to the floor. I feel like a flare nut will just skip and strip it.

 

[j91z28d1]

literally nothing good about that. lots of penetrating oil and the best line wrenches you can find. cross your fingers.


such a bad place for it.

 

[cofferson]

literally nothing good about that. lots of penetrating oil and the best line wrenches you can find. cross your fingers.


such a bad place for it.

I know. I'm even nervous about the line wrenches. I feel like even the best of the best snap on ones can't handle too much torque before rounding

 

[j91z28d1]

they do have some 360 deg wrap ones, I've not tried them. but they look useful. but I don't know if you have room.

https://www.napaonline.com/en/p/CHTLWFL4M?cid=paidsearch_shopping_dcoe_google

let us know if you find something that woks.