TSI 1.2 Sportrider - Spongey brakes

[SaracenUK]

Ibiza Sportrider 1.2 TSI 2012.
Brakes very spongey and brake pedal travels a lot, nearly to the floor on hard braking.
Resovoir full and no leaks, it is shared with the clutch master cylinder but clutch is working fine.
Bled all 4 corners starting with passenger rear, stripped rear calipers, regreased pad edges managed to get some lubricant under the piston seal so pistons wound in quite easily. Front calipers, disks and pads look OK but ran out of time to strip back.
Still spongey
Is it likely to be fronts or something else ?

 

[RUM4MO]

Well if you apply the handbrake firmly, that will remove the need for fluid to get to expand the rear callipers, so might help you work out what is going on.
From memory, you fully retract the rear pistons, then after everything is back together, pump out the pistons and hold the brake pedal down and apply the handbrake a few times.
Sometimes I feel, that "you" really try hard to imagine that there is a sponginess after working on brakes - just to prove everything is okay, it is just pity that we don't try to check the feel of the brake pedal BEFORE starting any of this sort of work and use that to gauge the feel at the end of this work. I've found that brakes can improve after a few miles and applications - after rework.
Out of interest, did you use a vacuum bleeder or a pressure bleeder?

 

[SaracenUK]

They were spongey and pedal nearly touching the floor before I started.
Did the old son in the car and push the pedal with bleed open, once on the floor, tighten the bleed, release the pedal and repeat,
Fair bit of fluid was pushed through at each corner. It does feel slightly better but nothing like the wifes FR
Might have to put the word out locally for a pressure bleeder.

 

[SaracenUK]

Stripped the fronts this morning, pistons pushed back easily, CeraTec greased the slide pins, CeraTec greased the edge of calipers and pads where they touch. Put it all back together and still bloody spongey with pedal nearly touching the floor.
Fluid in resovoir and no obvious signs of leakage anywhere.
At a loss now other than pressure bleeder.........

 

[RUM4MO]

One thing, if you have not already checked for this, if the fluid is getting back past the primary cylinder (being PC), then when the brake pedal is pressed down hard, the liquid level in the reservoir will rise slightly. I have not checked this with modern cars as I've never had a need to do so, but I'd think that if the primary cylinder is the source of your problem, then what I've written is correct.

 

[R3k1355]

How quickly does the pedal sink to the floor? If it's air in the lines it's usually quite fast. If it's leaking seals or a split in the line it'll sink to the floor abit slower.

Having the system shared between the brakes and clutch is a pain when trying to find a fault.