Sweet, so I got in the truck today to come home and while stopping the brake pedal sunk about an inch every other second. Acted fine at next light. Drove a little while, had to pump again to stop, then acted fine. Not losing any brake fluid so this tells me master cylinder. Anything else you can think of? No fluid around any fittings, drums, or wheels. These master cylinders hard to replace or pretty easy? Any input would be appreciated. 460/ 4 speed f250 4x4. Thanks in advance guys!