Brake Issue - Diagnostic Help Required

I have a 2008 Jimny ABS VVT with an issue that  we can't quite get to the bottom of.

Symptoms:
Breaks very spongy and foot to the floor almost before we the brakes seem to work. Pumping the brakes seems to give a better outcome , but once you take your foot of the brake to re-apply, then pressure has gone.

New oil, New lines, New pads, shoes and disk all round.

It is symptomatic of air getting into the system and bleeding doesn't resolve the issue.

Also can anyone identify this part that sits below the ABS unit on the near side of the engine? 

Thanks in advance, Colin.

 

Could be a bad wheel bearing allowing the disc to push the pads back meaning you have to take up the excess each time?

arthursc wrote:

Also can anyone identify this part that sits below the ABS unit on the near side of the engine? 
 

Valve assembly, proportioning & differential.

You say new discs all round 
So you have rear conversion fitted? 
Did you unbolt the rear caliper carriers and spin it round the disc to put bleed nipple to the highest point for bleeding 

Lambert wrote:

Could be a bad wheel bearing allowing the disc to push the pads back meaning you have to take up the excess each time?

Generally speaking, this will cause long pedal travel, but not a spongy pedal.  In 50+ years, I've only seen one occasion on which a spongy pedal was not caused by trapped air, and that time it was a brutal "hack job" with butchered pads. 

We’ve isolated the rear. Blanked off as part of the diagnostics. Still happens with the front. Servo has good seal so not that. Pointing towards the master cylinder.