97 F-250 when i start my truck the brake light stays on for 10-15 seconds and i have a very hard pedal until light goes off any suggestions on what the problem may be? ( maybe a brake booster going bad) the fluid level is fine and the pads and shoes are in good shape

 

May be normal....but also might indicate the vacuum pump is getting weak. Check for vacuum leaks.........

 

like itfox said if you don't have any leaks (rubber hose, booster) the vacum pump is getting weak.