Add oil to the various parts as you are putting everything back together. Some goes in dryer, some in the condenser and most in the compressor (if it is a Sanden unit). After you button everything up run a vacuum for at least an hour and then charge with the correct amount of refrigerant.

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Jim

Pressure test the system with nitrogen
Pulling a vacuum is not an adequate leak test
The system in my 124 wagon will hold 100psi all day
It will leak down from 150psi to 100psi in a couple of hours
30" of vacuum is equivalent to about -15psi