I have been working on a 1999 Buick Century Custom that had rusted brake lines. I get strange pedal feel that I will attempt to describe:
From 0% to about 15% depression, there is resistance and most braking force is generated
From about 15% to about 70% depression, there is less resistance and no braking force is generated
From about 70% onwards, brakes feel normal
I am looking for insight into the cause as well as a solution. On this car, the two rear lines each have a floating portioning valve (Dorman 905-952). This car has ABS, front discs and rear drums. Recently I changed all brake lines and replaced one portioning valve (it had been deleted by the previous owner). I have bled twice (RR, RL, FR, FL). When I bled, it was not level (sitting on a jack with tires off).
I have checked for leaks on the new lines, no leaks found. The wheel cylinders don't leak. I want to also say, the car seems to stop just fine every time (just requires a lot of travel).