Mine is a 7.5 liter, HD F250 '94 bought in Nov. of 1993. The brakes work fine -- strong lock up if needed. But after a solid lock up the peddle will slowly sink to the floor.

Is this normal?

Thanks, Pete

 

Nope, the pedal shouldn't sink. That indicates a hydraulic problem of some sort. A leak, bad master cylinder maybe. If you're losing fluid, it's obviously a leak. If you're not losing fluid, then it's the master cylinder.