How do you bleed the ABS unit. on 1995 Chevrolet S10

Brake peddle sinks when driving. Have changed the master cylinder. Bench bled master and each wheel. problem continues.

Asked by for the 1995 Chevrolet S10
With a couple of clamping tools, long nose vice grips will do, pinch closed BOTH the front, flex (rubber) hoses, pretty tight, it wont hurt the hoses. Now try the brakes, good high and hard pedal now? Also, pinch off rear flex hose, good high and hard pedal now? Post these results for more help! This WILL find your problem, it's old school but STILL works every time, for all of them, ABS or not! No need to have the engine running, just wasting gas. REMOVE ALL CLAMPS BEFORE DRIVING!!!
2 more answers
Does the peddle do the same when engine is not running. If it only bleeds down while running, and doesn't with engine off, Change the booster as well. If it was a '96 or newer the Tech2 will do that procedure of bleeding the ABS.
have it power beld by your mech