I have bled them. I replaced the fluid. I replaced the front pads (they were very thin) and still the pedal doesn't seem to engage the brakes until about half pedal down. When the truck isn't running the pedal is hard yet while idling it seems to engage at half pedal. How can I test the brake booster or master cylinder to see if they are defective? Or, what are the symptoms of a bad brake booster or master cylinder?

 

This is par for the course. Check the old threads, there is info on this there. Start 2-3 weeks ago.

 

if the pedal gets softer when running,the booster is good...

could wel;l be the m/c

 

What year is your truck? Some older trucks just had a spongey pedal, it was nomal.

 

if it doesnt feel right after bleeding its either the master sylinder or a problem with a brake line. if it gets softer while running you know your booster is good.