power brake problem

It's an F-250. 1989. Just touching the brake pedal will lock the brakes up in the extreme of this problem. Other times the brakes engage and lock up and I must use a toe to pull the pedal back. Sometime I can push the pedal in and the brakes will hold, again I must use my toe. Sometimes the pedal will slowly return up. Intermittant problem, sometime they work well. I have given the pivot a shot of 40 and that seemed to help a bit. Also shot the rod where it passes through the firewall. Thought that driving a bit in reverse might help but it didn't. Also a sort of squishing sound when I pump the brakes.

It's an F-250. Just touching the brake pedal will lock the brakes up in the extreme of this problem. Other times the brakes engage and lock up and I must use a toe to pull the pedal back. Sometime I can push the pedal in and the brakes will hold, again I must use my toe. Sometimes the pedal will slowly return up. Intermittant problem, sometime they work well. I have given the pivot a shot of 40 and that seemed to help a bit. Also shot the rod where it passes through the firewall. Thought that driving a bit in reverse might help but it didn't. Also a sort of squishing sound when I pump the brakes.

what year is the truck??
have you pulled all wheels & checked the brakes??