I'm redoing my a/c system and keeping it R12. The original R4 compressor is currently in the car and has the typical front shaft seal leak. In addition the system has a pressure switch leak, expansion valve leak and some hoses that need reworking.

I'm going to take the compressor from the wrecked car and use that since its 3-1/2 years young. It was a new R4 compressor and the system in the old car was retro fitted R134. I think the oil in the old system was Ester (could be wrong).

What would I use to flush the old compressor of ester oil in anticipation of going back to mineral oil? Can the compressor be turned in order to completely flush, while out of the car and without the clutch being engaged? I have read that perhaps I just need to flush it with the oil that will end up being used with the R12. A couple of complete flushes back and forth?

Also.....don't use flush fluid or thinner in the compressor?

Is there a better synthetic oil to use in place of the standard mineral oil.

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84 300DT Puke Yellow. Totalled after 438,000
84 300DT Orient Red. 169,000 (actual mileage may vary)
2002 Explorer EB (wife's)