I have a 2003 Ford Focus. I decided to change the brake pads myself, as they were worn out (especially on the left side). I replaced the pads on the left side and drove a little to test them out (1–2 km) and then came back home to replace the ones from the right side too. After doing so and going back out to test, I found that the brake pedal was very soft. The car still brakes fine, but I don't like how it feels. This happens with the engine running. When the engine is off, the pedal is hard after a few pushes. Any ideas?
A number of things could have happened:
You let air into the system, either by pushing the piston out too far or by un-doing the bleed nipple.
The system has developed a leak. You could have either damaged the seal when pushing the piston back in or by damaging a pipe by letting the caliber hang or by crimping it etc.
You could have put something back together wrong so when you push the pedal the caliber is actually moving away from the disc rather than pushing the pads into the disc. Ive seen it before when the wrong size bolts where in the sliders causing the caliber to move out / twist when the brakes were applied.
There is an adjustment you can make by turning the. Rear caliper piston counter clockwise (Ford Edge) back to the desired position about a 1\16 of an inch before the pad . I had to fix the rear pads the clips were absent rattling and such, on fords you can push them in too far, thats probably why the rear pistons have to be turned instead of pushed.