Brake help pleaseeee!!!!

Master cylinder help

Hi. I have an 87 cherokee 4.0. Recently I took the rotors off to machine them, but they were too skinny, so after I put the rotors and calipers back on my brakes didnt work! For some reason the brakes hold only slight pressure. I found that the driver side caliper was bad so I replaced it. That didnt solve the problem so I replaced the master cylinder. After I bench bled the master cylinder it held pressure fine. Then I connected the brake lines and bled all 4 brakes in the correct order, but it still only holds slight pressure. I have no idea what the problem is, except maybe that the bledder valve on the new caliper is on the bottom of the caliper and not the top like normal. Please! PLease tell me what you think could be the problem. I am so frusterated. Thank you in advance.
-Patrick

if the bleeder screw is on the bottom, then it's either the wrong caliper, or if you replaced calipers on both sides, then you probably put them on the wrong side.
bleeder needs to be on top.

that's most likely your problem, cuz it's not getting bled properly.

You think that 1 caliper not getting bled properly could cause all this trouble? You could be right but I dont know that seems like a small issue. Dam schucks gave me the wrong caliper
KEEP THEM COMING! THanks
-Patrick