2000 Honda civic ex. A couple months ago while driving I heard a squeal and my AC was blowing hot. I just changed out my expansion valve, drier and compressor but when I hooked up my guage my low side wouldn't build pressure and my high sat like 150. Finally the low side got to 20 and high about 200. I over filled trying to get low side right and when I did get it to 40-50 my high side would be 300 but it wouldn't hold. I emptied the system but 150 psi is somewhere in the high side and won't get out. Any ideas?