At first I thought you meant you somehow sucked an o-ring into the charging port but now I understand you opened the large union while the system was still under vacuum and sucked in the o-ring at the union, right?

You can access the other end of the hose from the bottom of the evaporator above the passenger footwell and blow back through it from there, it is not that hard to do. I just replaced that hose on my wagon and it is not hard to remove it if you have to...takes all of about an hour to pull out the battery tray and air cleaner to get it out but to blow back through it you don't even have to do that. The hose gets smaller in diameter and I would bet the o-ring is stuck in the rubber hose somewhere between the union and the end with the metal fitting.

This is why I like those little 2 oz oil charges...no muss no fuss with opening the system to add it.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz