HELP With Brakes.

[Grantkat]

OK everyone. I need help and suggestions (short of wheres the nearest junkyard) and hopefully my volvo crew here can help...if this is not allowed please let me know and I apologize....
Transparency - this is not an issue with my volvo. However the brake systems are basically the same. I am on a forum for the vehicle (my daughters car) and as opposed to Matthews, you get zero responses or if you do get one it is useless or plain stupid. (sorry for venting)
I am hoping someone can make some suggestions about how to troubleshoot or diagnose.
The vehicle is a 2003 GM trailblazer with a GM inline 6 with 4 wheel disc brakes. the system looks very much like my S70 system. The pedal went to the floor on her. I just replaced the master cylinder. I bench bled it and it pumped fluid just fine.I installed it and used a vacuum to pull fluid through the lines. 3 of the 4 wheels are not pulling fluid. at best its a trickle. One line seemed to be pulling fluid fine in other words a solid line of fluid. the others no. I buttoned everything up and tried the brakes. NO change-- pedal to the floor when the vehicle is running. I do get resistance from the booster. but the minute you start the car the pedal easily goes to the floor. I hooked up a tube to the bleeder valve on one of the front wheels and had my wife push the pedal. 3 inches of fluid into the line and then nothing, no matter how many times pumped..that was it.
I realize this is not a volvo but again the systems look very similar...
Can anyone offer some suggestions on where i can look and try to figure this out?

[ZionXIX]

Without knowing trail blazer anatomy, I would be concerned about bad brake hoses collapsed internally or air trapped in the ABS system if it has one. Typically a bad brake booster should have a hard pedal as there is no vacuum assist to help. I find the power bleeders are far more convenient than vacuums to do one man brake bleeding. Are the calipers siezed? Was the old fluid really burnt and full of debris? Does this vehicle have any proportioning valves between the front and rear brakes that adjust fluid pressure?

[hausmeister]

Pedal to the floor would mean either air in the system or fluid loss, right? On the other had you say you cannot bleed the system which makes it sound like the lines are clogged (bleed from furthest to nearest to the master cylinder). It should still bleed even if the calipers are seized imo.
How was the system maintained, regular fluid changes, hoses in good condition? Lines rusted?
I'm not sure where you need to start looking, probably you would need to check everything as this does not sound safe.

I agree a pressure bleeder makes this much easier, but it should work just fine with pumping the pedal. Depending on the service history I'd probably either replace all wear items first, or try to troubleshoot where the fluid is being blocked.

[volvolugnut]

Do you have a service manual or online information on brake service for this vehicle. There may be a proportioning valve that must be adjusted before you can bleed all wheels.
volvolugnut

[Grantkat]

I think you guys are on to something....
First the lines are good, no rust and all are solid.
there is an electronic ABS module and attached to it is an ABS Pump. All lines go through the pump. I am betting thats where my issue is. if that pump is bad or full of air thats a single point of failure...I am investigating and will keep you posted...thanks for the ideas...

[matthew1]

Maybe it has stored codes pointing to ABS module, or something else...

[Grantkat]

I put a reader on it and no stored codes for ABS. Other than codes for front right wheel speed sensor in history (replaced that a few weeks back.
no codes set for the module or the pump.

[abscate]

You might need to open the valves on the ABS module to bleed a fully drained system ftom scratch. In Volvo world there is a command in VIDA to do this.

Maybe scour the Chevy Fora for that info? The good thing is GM is everywhere so you don’t have to rely on a quirky bunch of Volvo owners , it should be out there.

[scot850]

Does your scanner actually check for ABS codes? Many more basic scanners you only get engine codes and if you are lucky, maybe trans codes.

Neil.

[Grantkat]

I rented a scanner that had ABS. The only ABS codes were related to the wheel speed sensor and were historical as opposed to current.
To bleed the ABS pump you need a bi-directional scanner with an ABS Bleed option. The scanner I rented reads coes but didnt have the operational bleed option.
Abscate, I think you are correct.

for reference I did a deep dive on the system. its a 2 port Master Cylinder. Both ports go through hard lines to an ABS pump located on the frame rail, driver sider just under the driver door. The ABS pump is a 5 port electrically driven pump, 2 input ports from the master cylinder, and 3 output ports for the brakes. The front brakes each have their own separate port. The rear brakes have a common port.

Abscate - I wish what you said was true....however what you find is a lot of here is how to do it, with not alot of information on specifics you might need to know, like watch out for this, or be careful of that. Its the small simple things that can turn a quick repair job into a 3 day nightmare.
it's the personalities of the members. Here you feel like people genuinely want to help. I literally have gotten "Good Luck on that and let us know how it goes" more than once on other forums and like you I thought there is a ZILLION chevys out there, someone has got to have some info or advice on this...48 hours after posting, and dozens of reads - no reponses. that blows my mind..

ok you are going to laugh (or maybe cry) - I kid you not. After asking for the port configuration and not getting any responses, I did my own research and found it. It wasnt that hard. I then posted it as an FYI - got over 2 dozen responses back from other members...saying "thank you! and things like "been looking for someone to explain that forever". Yikes...is all i can say.