Audi TT Brakes problem

[Gunny112]

Can anyone shed some light on the problem I have please. I am driving along all ok and the brakes are fine but after a while when operating the brake pedal it goes soft and spongy and goes all the way to the floor softly! the brakes work! If I turn off the car and leave it for a bit they go back to normal operation, its like im losing brake fluid but im not if you see what I mean. could it be the ABS Sensor?

Also any tips on rewinding the window wire back on the wheel I get one on then the other doesn't seem to fit once wound on Grrrrr

Any help is a bonus guys and girls Thank you

Gunny

[Gunny112]

Thank you KELL for the info but that is not the problem im experiencing. it seems when ive been driving for a while and the engine is warmed up its only then the brake pedal goes soft and spongy on me. if I pump the brakes the pressure returns to stop the car??

[Gunny112]

I had a rear calliper fitted back last month and soon after the problem started. the brakes work ok but after a while the pedal goes spongy and goes softly to the floor when pushed and the ABS light comes on. from then on I have to pump the brakes. I cant see any fluid loss or split pipes anywhere? its like it loses all pressure.