Quote:
Originally Posted by 87tdwagen
Speaking of flushing and ordering parts ect. Do any of you see any concern in my drawing the system into vacuum for leak testing purposes (after evac of course). Do I run any negative risks in drawing the system now in it's current state? moving crud etc.
I would like to know if anything else is leaking before charging after all the work. My sniffer has not detected any leaks, nor can I see UV dye traces around any of the components nor thru the center vent, although that's the extent of access I have for the evaporator.
Thanks for your great advice
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Leak testing is done under pressure, not vacuum. The lowest pressure the system will ever see is on the low side of the compressor, typically 35PSI or so above atmospheric pressure. The vacuum is done to dry the system, not to check for leaks. Even the best sealed automotive HVAC systems will only pump down to ~1000 microns of vacuum just due to the various shaft seals, O-ring joints, and other parts that are designed to retain pressure and not vacuum. If you want to do it by the book, run a nitrogen sweep, then pressurize the system to 200PSI standing pressure and monitor for at least an hour. If you have a tight system, the pressure will not move even 1 PSI. Pressure testing can ONLY be done with nitrogen since it does not change gas pressure with atmospheric temperature.
Don't waste your time pressure testing your system as it is now. You're replacing a bunch of parts. Only pressure test and leak check when you have it reassembled and ready to go.