When my car has been driven for a while and everything is at operating temperature. Under light braking when speeds decrease to say 40km/h I can hear a metal scrapping/grating noise, not the low material indicators... The discs are fine there is no pulsating.
If I coast in a car park and lighlty apply the brakes the noise is there, very loud. If I pump the brake pedal at idle there is a squishing noise (ie: if you squeeze a detergent bolt that is empty lightly it will be a sound like my brakes are making, that appears to come from the mastercylinder. The calipers creak also.
My thoughts are that there is alot of air in the system and that the pads are not being pressed against the discs firmly enough, hence the grating/scraping noise.
I am up for suggestions, I believe new pads/bleeding might fix it but if you know or believe that it is something else then please comment!