When I do a compressor- there is the expansion valve and dryer- those o-rings plus I replace the schrader valves since they are cheap and one of the most common leak points.

Flushing- I ussually do one part of the system at a time, so basically take things apart at the joints. Then I use Naptha or Acetone (1-2 quarts) and blow a plug of the liquid through the system. These both are nice and will leave a slight oil residue which will prevent corrosion.

Do it again and again with the flushing until it comes out clean. I use a jar/or can to ketch the residue with rags stuffed in it. 1-2oz plug with compressed air behind it.

Put fresh oil in each component or close to them, per the factory guide.
If I had a problem child with several compressor replacements- I'd be thinking "black death" and check. When I did mine, I found a large piece of aluminum upstream. It was quite amazing.

Michael

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Michael McGuire
83 300d
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD
86 300E