[Shotimes] What does it mean when you can't bleed one of your calipers?

[Tony Fratzke]

I was replacing same pads and rotors last night and i wanted to bleed my
brakes because my pedal felt a little spongy.  All was going well until
i tried doing the the left rear.  I had to push will all my might to get
the pedal to move at all with the valve open.  The fluid came out very,
very slowly.  The pedal went to the floor immediately on the other
corners. Also, this brake seems to make noise a lot while driving slow.
Does this mean the piston is shot? Bad line somewhere?  How to
troubleshoot?  Also, my left front bleeder valve is frozen.  Can i use
heat on it to try and break it loose?  Thanks!
 
Tony Fratzke
93 ATX