94 probe gt clutch problems

whats up every1 i put in a new slave cylinder and bleed it out an got pressure back in my clutch drove it down the road to inspect it and then it just loses everything idk what it is. could it be the brake master cylinder or one of my friends said i had to bench bleed it or it would lose pressure like it did idk if any1 can help thatd b awesome ppreciate it