My slave went bad once. Installed a new one,bled it. Worked great for 3 hours. Then the master went bad. Couldn't handle the pressure I guess. If one is bad just be ready to change both. I hope not because they sure don't give those away. They were the original ones in my '88 and had 250,000 on them so I couldn't complain. Except that it was the same day.:***: