rangers are very hard to bleed.
This guy is on to something although gravity bleeding did NOTHING for me. The ranger Master cylinder points down so the air trapped in the Master floats up away from the bleed ****** on the end.
A pressure bleeder on the master reservoir will help.
Leave the lines connected to the master but unbolt it from the firewall. Try to position the master as level as possible while it's loose from the pedal & firewall. Jack up the front of the truck and support with jackstands to raise the bleed ****** end of the Master. Bleed Master using a dowel rod (this usually takes 2 people since you can't really move the master away from the firewall much.
Once you feel like the master is full of fluid bolt it to the firewall and bleed bottom of the line (the line has a spring loaded check valve), then snap that into the slave line and bleed the slave.
When I did the clutch & hydraulics in my 2.3 with an M5od it took be 2 days of messing with the hydraulics to get it bled. Listed above was simply the resolution to my issue, skipping all the stuff I tried that didn't do jack.
Obviously since my truck is a 2.3 M5od the slave cylinder may be different. You might not have the check valve line, but the master is going to be the same...
Good luck.