just changed the front brakes on my s80. They are really mushy now..I have to push the pedal a long way before the brakes catch. I assume I have to bleed the master cylinder? or is it something else. I was going to just bleed it anyway, but then i figured i'd see if anybody knew anything else it might be.

 

Take it out on an abondon road and at about 40 MPH jam on the brakes to activate the ABS and see if it gets better after that.

Also I have seen this happen from aftermarket brake pads.

But try the first thing first.