Brake Pedal still spongey...93 Sierra
 

Bought a 93 Sierra. Prior owner said they tried to bleed the brakes over and over. Pedal felt like primary piston was failing, secondary kicking in. Thats where it catches with initial push, then fails then re-cathces. I replaced the master cylinder and have bled them three times. No better than before the replacement of master cylinder. Do I have bad calipers? WTH?

Not sure with the "newer" stuff. Is there a porportioning valve on the MC?

If you bleed them and there's still no pressure your calipers are worn out and exhaling to much. Check to see if the pads are in slight contact without the brakes on. If not you probably need new calipers.