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Brake Pedal to the floor after new calipers, bleed, flush and auto shop bleed

:help:
Old thread,but I am experiencing brake peddle fade all of a sudden on my 02 z71.
Don't use the truck often anymore and it was running fine before the issue started.
Went on a dump run with the misses last week and after a few stops noticed the peddle going to the floor and braking getting worse. I did top up my fluid as it seemed low. Made it barely to my destination and home with a very hard to stop truck. Pumping didnt do much, and the e brake didn't either.
Get home. Fluid level stays ok, start pumping in the driveway. With engine running, she goes to the floor and brakes barely work. Engine off, peddle gets stiff after two pumps.
No leaks anywhere to be seen.
Tonight I tried again, same thing. No loss of fluid. But no brakes.
Thought, maybe bleed her to be safe, but front bleed screw snaps off, and rear one strips the head.. Like I said, don't drive it much so its been a few years since she's needed brakes, or bleeding.
So, aside from needing to drill out my bleed screws and install new ones, thoughts on my root problem? How can you isolate vacuum boost issues vs master cylinder failure?
Thanks av lovers.
This is a new one for me. Never had a complete brake failure like this without obvious cause.

 
Replace all of the fluid in the system while bleeding rears then fronts.

You may have moisture or air in the system...

Synthetic brake fluid is awesome but collects moisture.

If you have a low fluid level it is likely you have a minor leak somewhere and are getting air into the system. Maybe refreshing the fluid will help. If you don't use the truck often use standard brake fluid and not something like the valvoline synthetic which is awesome but needs to be changed yearly to perform well because it absorbs moisture like a sponge.

If this doesn't do it you will have to go further... Check for leaks and sticking caliper pins...

Rodney
 
Thx for the reply Rod.
Was able to get the fluid refreshed today, was pretty dark.
Still with key off, or key on, eng off, I get better brake peddle pressure, but will slowly go to the floor. And if she's running, to the floor easier and no stopping power..
No leaks that I can see and if I sit there pumping, no loss of flood..
I so have to replace and drill out my bleed screws on two though.. Any idea what thread those are?
Thx all.
 
Sounds like a bad master cylinder.

There would have to be a leak for air to get into the lines of the previously closed system. A little air will give a soft pedal, but repeated pumping, even with air in the lines should still give some pedal provided there is no fluid leak; it will be soft and maybe even sink to the firewall on a hard push, but soft or hard, it will not slowly sink to the floor.


If fluid level is constant in the master cylinder, and there is no fluid loss at any wheel cylinders or the anti-lock pump it is likely an internal leak in the master cylinder and changing fluid will not help much if at all ..if so, repeated pumping should bring up the pedal for a second or two and then it slowly fades to the floor.
 
So still no brakes.
I replaced the master cylinder and both rear calipers now.
Was able to use the one man brake bleed kit to bleed the rears well but when I tighten everything up still no brake pressure.
With it not running there is some resistance, but when running it goes to the floor much easier.
Haven't bled the fronts as I didn't disturb them and figured I should have something by now.
Even if the brake booster was shot, I would still have brakes. Wouldn't I?
Getting frustrated here. One of the front slippers bleed screw is stripped so I was hoping to avoid replacing them too but if its the only way to eliminate air in the system,, so be it..
Any other ideas are welcomed..
Regards,,
Mike.
 
I know this is a very old thread, but I'm wondering if anyone ever found the solution ?  I did a search since I had the same issue just yesterday and I found a solution. Maybe it can help other ppl.
So I changed my fromt brakes and front passenger caliper , put Everythjng back and bleed the front brakes at the valve and another person helping pumping the breaks.  I bleed them about 25 times and I still kept getting air in the lines.  The pedal would newel good but as soon as you turn on the truck the pedal would drop to the floor and I he 0 break power. 
: how I fixed the problem -  you need to bleed the breaks while the trick is on (idleling)

With the truck on I bleed the two front calipers two times on each side and now I have a firm break pedal.  Hope this helps someone else.  I tefused  to believe that my master cylinder,  booster or Anthing else broke at the same time I changed out my caliper.  This was on 07 Avalanche
 
Look on frame under drivers seat for oil
GM used cheep brake lines and rust out there first
Sue them tards lol
Get a gallon of brake oil and get wife to pump up brakes 3 or4 times push one hold peddle crack bleed fitting just to release pressure
If no pressure them master toast I say. When bleeding!
Just a little air in line cause peddle to go to floor
 
Thomcat - Great suggestions which I am still going to consider getting doing a larger bore MC with Hydroboost mod later, but I think discovered something last night that no one (including the brake service shop and the local Chevy "stealership") noticed or guessed... :laugh:

While I am more than a little embarrassed to admit this, my experience might help someone else... I think I inadvertently switched the right and left calipers and installed each on the wrong side. Why do I think this... because the bleeder screws are at the BOTTOM of the calipers - not the top where they are supposed to be. So no wonder I am getting no air bubbles on my bleed... because the air is "trapped" at the top of the caliper and the fluid is denser so it exits the caliper from the bottom not allowing the trapped air to escape.

MS03_2500... I have a 2002 Avy 1500 Z71 with newly (albeit "wrongly") installed GMT900 Mod using Centric calipers & Eline Drilled Rotors and Pads for a 2007 Tahoe.
Unfortunately, I found myself in the same position. I inadvertently reversed calipers. I can’t tell you how much this post helped me. As soon as I reversed the calipers, I was able to bleed the system. Many thanks!!
 
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