I am currently restoring a 1987 Nissan 300zx
I replaced the master cylinder and when bleeding the brakes the pedal would hold for a few seconds and then slowly fall I ran about 2 liters of fluid through it and determined that the master cylinder was defective and returned it for a new one
I bench bleed the new master cylinder and installed it and ran about two liters of fluid through it my previous issue was resolved but when I hit the brake pedal it is soft but doesn't go all the way to the floor after two-three pumps it feels as it should let it sit for 30 seconds and I have no breaks until pumping the pedal.
There is no fluid leaking anywhere and I am getting clean fluid out of all four calipers (new breaks right around) I have also played with the adjustment on the brake booster and still, nothing calipers are on the correct sides as well
Replaced all flex lines still unable to bleed brakes