Mushy brakes 4 life...

You probably know this, but just in case:
first; I will assume the hydraulic system is fully bled and fully functional.
Next, assume the rear wheel cylinder pistons are free to move waaay out,past their design range, but not so far as to fall out.
>The master-cylinder is now operating as if the rear system has failed. So the entire guts of the M/C has to be pushed to the end of it's travel, until the frontmost piston hits bottom . Not until that moment does the fluid begin to move out to the front calipers.
If the front system is in perfect working condition, it will now have a hard pedal, and braking can begin, using the front only system, allbeit with a very low pedal.
>But if the pedal does not get hard, then there is additionally,something wrong in the front system. Remember I assumed the hydraulic part was perfect.
So, I know that now I am in deep chit, because I assumed the hydraulics are perfect.
So now I have to find out why I can't get a hard pedal, down near the floor. At this point I no longer care about the back. I have a decision to make; Do I; A)continue to believe that the hydraulics are perfect, or do I. B) take everything apart again, and go hunting for a mechanical issue?
Well I'm gonna go with A) on account of I have already bled the chit out of it.
So, off with the wheels and off with the calipers. Now, I take big C-clamps and force the pistons all the way back and lock them there. Then I retest the pedal. >If I now have a hard pedal, then I know that in fact the front hydraulic system is fully functional, and therefore I must have a mechanical problem. And we'll get to that later. But for now, I can continue on the rear diagnostic, leaving the calipers so locked.
>But if the pedal is mushy with the pistons clamped, I have some more work to do on the front system.And it's gonna be a hydraulic issue. I go find it, fix it, and retest the on-the-floor pedal. I can't attack the rears until the pedal is hard.
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So let's say you finally have a hard pedal
Now we move to the rear, Take it all apart,including the push-rods, to access the W/Cs, and put clamps across the metal pistons, preventing them from popping out of the bores. Now go look for a hard pedal again. The pedal should take a couple of pumps to pop up, and then get hard. This proves that the compensating port is open and working and most importantly, that the hydraulics are indeed 100% working. But if the pedal doesn't get hard.......now you at least know where to look. And if the pedal doesn't come up, you look to the pushrod length and why the C-port is not working.
>But suppose you did get a hard pedal. Now we go to the back, and have a good look at the parts, and why they don't like to be adjusted up tight.
And the guys have covered that pretty good already.
Once you get the rears up to speed,and everything assembled in their proper working relationships, and the pedal gets hard....... then you return to the front. Reinstall the calipers and check the pedal. If hard, put all the wheels back on, and roadtest.
But if not hard now, then you know exactly where to look. You have a mechanical issue, and very likely it will be easy to spot. In all likelyhood one of the calipers is flexing. It could be a bent pad or a problem in the caliper mounting system.
In any case,you're on the home stretch, and you will find it.
Do not drive it until you have a hard, high, pedal, please.