Hey, my 86 s10 4x4 brakes give out almost completly while driving just for an instance, then after letting off the pedal I have brakes agian. brakes are less than year old and I replaced the master cylinder thinking it would solve this problem, my brake have not failed me since the new master cylinder, but the pedal feels soft like normal for the first half of pedal travel with good braking, going past half way on the pedal travel it gets very firm and braking seems to fade a little. mostly the pedal feel to hard to push after half stroke. please help.