Y Reg 2001 Audi A3 100bhp TDI Put the new caliper on today, fully bled the system. Including the master cylinder. With the engine off, its firm as you like, rock solid from the top. With the engine on it's spongey. Also if you keep your foot on the brake, it goes to the floor and eventually the revs dip. This leads me to think there is a vacuum leak. I've disconnected and sealed the branch off from the valve just after the vacuum pump. But it still does it, so this would suggest the leak is on the solid pipe to the servo, but i find that hard to beleive. Anyone had this before? Cheers in advance.