Your 99 f150 about every six months the pass side rubber hose locks the brakes up what could it be?

Brake Hoses Deteriorate On The Inside And This Restricts The Brake Fluid From Returning To The Master Cylinder Which Causes It To Keep The Caliper From Releasing From The Rotor Like It Should. If You Are Sure It Is The Brake Hose Change It. It Should Solve The Problem. But From I Kinda` See Here You Would Or Should Have Had This Changed Already Only For This Problem To Began Anew. If This Is The Case, I Would Think You Have A Problem In Your ABS Brake System. Have The Codes Ran On Your Truck And See If This Shows Up To Be The ABS System Good Luck