i've had J30 front calipers and rotors on my s13 for a while now and have not been able to get them to bleed. i've tried a new master, rebuilding the calipers, gravity bleeding them and pump bleeding them to no avail. when you try to brake the car the rears lock up and the fronts don't do much of anything. there doesn't seem to be any leaks anywhere in the system that i can see. does anyone have any ideas on what to try next? i'm at the point where i'm about to just run stock calipers and s14 rotors if i can't fix this.

 

if you rebuilt them, and you know you did that right.
and you have a new master on there that you know is working properly,
and you've not been able to find any leaks anywhere,
then more likely than not, you just have air in the lines.
When the calipers are off of the rotors, and you push the brake pedal, do the pistons come out properly?
Can you pump them out a little bit that way, and then squeeze them back in?
Does anything change when you do that a few times?
Are you sure that the front calipers are not functioning and it isn't something dumb like the pads are crap? They could have soaked up some oil, or even been glazed over and just not producing any stopping power. (it can happen, but usually you get some kind of sequel, whine, some kind of noise.

 

Whenever I have had this problem it's typically a bad line, or a bad master cyclinder, even if it's new. I was rebuilding a Ford RS200 that had been sitting for years which has twin AP Racing masters, I replaced them with brand new AP masters and still could not get the front to bleed, ended up I just got a bad new master from AP. I would also try to reverse bleed them, if you reverse bleed them you will know 100% that you have gotten all the air out of the system.