magnum 49

If you have braking problems with pedal going to floor on Chevrolet trucks and GMC'S try this. Crack your bleed screw and observe your brake fluid flow. If there don't seem to be very much pressure then nine out of ten your master cylinder cannot supply enough flow/pressure. This low pressure will result from a master cylinder on trucks up to 2001 (chev) 2000 (gmc) . Buy a master cylinder newer then 2001 or even a used one and you will be astounded at the difference in flow/pressure.
I have a 1998 cheverlot Silverado and put 4 master cylinders on it, new brake lines, wheel calibers, pads, abs module, computer automatic bleed and no result until I replaced my master cylinder with one from a newer year 2001 (chev) or 2000 (gmc)
ps: One other thing,if you find you have no brake when driving slow and coming to a stop, remove your abs wheel sensors and clean the base metal ,shims, then use a light lubricant and tighten in place.
If you have success with this please comment on this post as to your findings