I am new to this site and have purchased a 1980 240D. The work on this car has become a labor of enjoyment. I am going to replace the AC compressor, drier,pressure switch, and expansion valve. I am use to seeing a pivot bolt and slide channel this set up is different. How do loosen the AC belt ? It takes a GM radial R4 compressor and has been retrofitted with R134-A. Any do's and don'ts? Should I flush the system before or after replacing the parts and recharging?

Thank You jcj