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2012 Chevrolet Impala LT
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Discussion Starter · #1 ·
I could really use some advice here please. So I have a 2012 Chevy Impala LT FE2 suspension. I have replaced the following on both front axels: steering knuckles, lower ball joints, wheel hub assembly, wire harness from speed sensor to main loom, sway bar link bushings, inner & outer tie rods with new bellows, calipers, high performance rotors and brake pads. I blead the breaks multiple times and was thinking I was missing air because with the car off it builds a little pressure but then as soon as I start the car the brake pedal falls to floor when I press on it. So I was assuming that it was the diaphragm inside the break booster but once I took the master cylinder off I don't see the diaphragm like it's on like a 2011 model. Does anybody know anything about this if there's something else I'm not thinking about or is there a check valve that I can check. I went on the Chilton's website and ordered a book but they messed my payment up and I can't find a repair manual for anything.
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Here's some pictures after I've removed the master cylinder I think on like a 2011 there's a diaphragm in that empty space there on the brake booster I was thinking it was that that was leaking but I can kind of hear some air when I push the brake when I had it all before I took it apart and is there something I'm missing or does anyone have a repair manual for a 12 Impala LT? Thank you for any help you all can provide.
 

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What was the level of Brake Fluid in the reservoir?
Brake Pedal's hitting the floor?
There's a Hydraulic problem; somewhere.
Do you see any evidence of a leak?
You should normally troubleshoot the whole kit and caboodle for a brake fluid leak after checking the reservoir and doing a perfunctory bleeding to see if hydraulic pressure can be developed.
 

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Discussion Starter · #4 ·
What was the level of Brake Fluid in the reservoir?
Brake Pedal's hitting the floor?
There's a Hydraulic problem; somewhere.
Do you see any evidence of a leak?
You should normally troubleshoot the whole kit and caboodle for a brake fluid leak after checking the reservoir and doing a perfunctory bleeding to see if hydraulic pressure can be developed.
Ok so the resivour was full. So before pulling the master off of the brake booster I had bleed the breaks or so I thought. I started at the rear passenger side and did all 4 brakes with a hose and bottle by my self probably 3 times. Then had a friend help me and went around twice. I felt pressure with the car off but then when I started the car and pushed the brake, it went soft. I do not see a liquid leak anywhere. The reason I thought the booster is because when I push in the pedal and it gets near the floor I hear a small click and what sounds like a spit if air. So I was thinking that the diaphragm had a leak but I don't see a diaphragm in this 2012.
 

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What was happening to the Break Fluid in the reservoir while the bleeding was being conducted?
Did any pressure develop at all?
 

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Discussion Starter · #6 ·
What was happening to the Break Fluid in the reservoir while the bleeding was being conducted?
Did any pressure develop at all?
Oh yes sorry. If I kept the vehicle off then yes I felt pressure build up through the pedal getting harder to press. I also could spin wheel hub and if someone hit the brakes it would stop, this is when the car off. I didn't try the wheels with the car on because that is then the pedal looses that pressure and sinks. When I was bleeding the brakes obviously the fluid level receded because of me cracking the valve but since closing all valves the fluid level has stayed the same.
 

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Discussion Starter · #8 ·
There's a procedure in the service manual regarding the proper way to bleed the ABS brakes and it's module.
Are you referring to the service manual that I purchased yesterday through Chilton but that I have yet to gain access to because they can't find my purchase. LOL They took $35 out of my PayPa Chilton which is now part of Cengage withdrew the money do hopefully I will have access today.
 

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Sorry to break the news but for that $35.00 you could have grabbed up the factory service manual on a CD-ROM from eBay. I don't trust Chiltons, too simplified with too few details.
 

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Everything you've done ... thus far, to check-for or eliminate any air bubbles within the system, ... considered. ✔︎
And, ... the behavior of the "Pedal" ... before - during - after ... bleeding the brakes, ... considered. ✔︎
The problem you've got there seems to be isolated at the Master Cylinder.
The Master Cylinder's Main Hydraulic Seal.
...................................
Where others may advise you to "Throw a rebuild kit in it!" ... I don't ever make that suggestion to anyone.
Not with Brake Master Cylinders. ✔︎
New Master. Bench bleed it before installing.
Then, ... bleed the entire system according to Hoyle.
Use only approved, fresh, clean, Brake Fluid from an unopened container.
Good luck.

"In general, whenever you are bleeding an ABS-equipped vehicle you do so exactly as you would any other vehicle - "Pump-up" the pedal to pressurize the system, ... HOLD, ... Open a bleeder, ... Maintain constant pressure upon pedal while it descends with bleeder open. Close the bleeder, and repeat." -- J.Walker Jr. / Team Walker

 

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I've been through this before, unfortunately if air gets introduced above the ABS system and there's no way to get rid of that air without it going through the ABS system it's probably best to pay a qualified mechanic to do it. That, however, should not result in a complete brake failure, if air gets caught in the ABS you'll most likely get spongy brakes, still a real problem but they would work at least somewhat.

So I am thinking, the rod or dowel from your brake booster isn't lined up with the master cylinder piston properly.
That one's a bit of a trick, to make sure that rod gets lined up as you install the master cylinder.
If it's not lined up right then it can't push the master cylinder's piston, instead it just goes into the space there is beside it and you have no brakes.
This is another that, it may be best to pay a qualified mechanic although it's not as bad as the air in the ABS. In most cases it should just line up on its own, however it is still always a good idea to look closely as the master cylinder goes into place, to make sure that rod is properly lined up before sealing that gap and tightening down the nuts onto the bolts that hold it all on.

You might try and partially remove the master cylinder, you may be able to just loosen / remove the bolts / nuts that hold it onto the brake booster and move it partly out while looking in there to inspect that rod's position, a flashlight might help and hopefully you don't have to disconnect any brake lines.
 

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"Master Cylinder. Master Cylinder.
You can do it!
Master Cylinder. Master Cylinder.
You can do it!"

AutoZone has them all over the place!
They got the ones them good old boys use for racing.
They got the ones just like yours, ... already fixed; and raring to go.
Plus, ...
They got the one's that chaffed everybody's ass when the brand moved-out of MoTown, ... if you know what I'm sayin'?
It does not matter one bit, ... which one you choose.
Every last one of them is better than what you're holding.
Haven't you replaced everything that you could get loose on that baby, already?
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Discussion Starter · #13 ·
"Master Cylinder. Master Cylinder.
You can do it!
Master Cylinder. Master Cylinder.
You can do it!"

AutoZone has them all over the place!
They got the ones them good old boys use for racing.
They got the ones just like yours, ... already fixed; and raring to go.
Plus, ...
They got the one's that chaffed everybody's ass when the brand moved-out of MoTown, ... if you know what I'm sayin'?
It does not matter one bit, ... which one you choose.
Every last one of them is better than what you're holding.
Haven't you replaced everything that you could get loose on that baby, already? View attachment 165129
Not yet but it seems I have begun. I don't want to be the guy who just replaced every part because I am unknowledgeable but I don't mind being the guy who replaces everything because it's easier than cleaning 10 years of gunk off the part. 🤣.
 

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Discussion Starter · #14 ·
So a little update this far. I did remove the master but will actually replace it later this week. I first just wanted to get in there and see if the booster looked bad. When I got in there it didn't have the diaphragm like previous models so without removing the booster I have no clue if it's bad. I am going to include some pics and a video if it will let me. The reason the video is because of something a person said about the piston not hitting the master correctly. But when I hit the brakes with the bat in and in drive the left axel stops and right side doesn't do I don't thing this would happen if it's the piston on booster. I'm not afraid to replace any part but at this point but knowing what it is I think I'm going to have a guy with a good computer with the ABS function come over to the house and diagnosis the issue so I can fix it.
 

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Discussion Starter · #17 ·
Sorry to break the news but for that $35.00 you could have grabbed up the factory service manual on a CD-ROM from eBay. I don't trust Chiltons, too simplified with too few details.
Really, dam. I found the service manual on ebay and it was like $400 but it was the actual books. I'm about to look for cd now.
 

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I find it hard to believe that somehow your brake booster or master cylinder failed right when you changed out other parts of the car. I feel like this is an Occams Razor example. You put new calipers on, and likely introduced air into the system that wasn't there before. The booster worked before you did this work, so the absence of a seal/diaphragm is not going to be the problem, right? I'd say get someone in there that can activate the ABS purge with a computer and bleed the brakes again. If you are really having problems getting it bled, you could try a Mityvac hand pump to assist. Make sure there are no air bubbles in the hose.

FYI, this is the bleed procedure:
  1. CAUTION
    Caution
    The Auto Bleed Procedure may be terminated at any time during the process by pressing the EXIT button. No further Scan Tool prompts pertaining to the Auto Bleed procedure will be given. After exiting the bleed procedure, relieve bleed pressure and disconnect bleed equipment per manufacturers instructions. Failure to properly relieve pressure may result in spilled brake fluid causing damage to components and painted surfaces.

    Raise and support the vehicle.
  2. Remove the tire and wheel assemblies.
  3. Inspect the brake system for leaks and visual damage.
  4. Lower the vehicle.
  5. Prepare the brake bleeding equipment and the vehicle for a pressure bleed of the base hydraulic brake system.
  6. Inspect the battery state of charge.
  7. Install a scan tool.
  8. Turn the ignition ON, with the engine OFF.
  9. With the scan tool, perform the following steps:
    1. Select Diagnostics
    2. Select the appropriate vehicle information
    3. Select Chassis
    4. Select Electronic Brake Control Module (EBCM)
    5. Select Special Functions
    6. Select Automated Bleed
  10. With an assistant ready, raise and support the vehicle.

  11. NOTE
    Note
    • Apply the brake pedal when instructed, using moderate effort.
    • Ensure the pedal remains applied until instructed to release by the scan tool.
    • Do not exceed the time period allowed by the scan tool for having the bleeder valves open.
    • The bleed sequence for each corner is as follows:
      • Left front
      • Right front
      • Right rear
      • Left rear

    Perform the automated bleed procedure as instructed by the scan tool.
  12. If the automated bleed procedure is aborted, a malfunction exists.
  13. After completion of the automated bleed procedure, press and hold the brake pedal to inspect for pedal firmness.
  14. If the brake pedal feels spongy, repeat the bleed procedure completely.
  15. Remove the scan tool.
  16. Install the tire and wheel assemblies.
  17. Lower the vehicle.
  18. Adjust the brake fluid level.
  19. Road test the vehicle while confirming the brake pedal remains high and firm.
 

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There's a few things you should have for doing Brake Fluid work.
One of these is helpful.
Especially, ... if you're doing a Brake Fluid exchange without replacing the Master.
Evacuating the MC reservoir of "Stale" fluid is a cinch with one of these.
Known to most wrencher's as: "'Lil-babies Booger Sucker's" ... an Ear Syringe is a handy-dandy tool for evacuating fluid from the MC... power flushing Carburetor Passages, squirting cleaners on things.

If you use it cleaning carbs or douching Throttle Bodies with Carb Cleaner; it will do he job.
But, ... Carb Cleaner does a number on the elasticity of the Bulb; rendering it useless afterwords.
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