Evacuation procedure.

[Tim]

I think this needs to be mentioned again. This theory you need to hold a vacuum for 24 hours to support a leak-free system is not really a great idea. Systems can hold pressure under a vacuum and not under pressure. The system can hold under pressure and not in a vacuum.

https://www.autoacforum.com/viewtopic.php?f=4&t=13603

[B52bombardier1]

Hello,

This is absolutely true and something I've recently seen on my 70 El Camino. It developed a leak so we pulled it down and it held vacuum very nicely. Then we added some refrigerant and it leaked liquid like a volcano at a bad fitting crimp. Yes, hard to believe with such a big leak under pressure but yes, seen it!!

Rick

[Cusser]

I myself observed a related/unrelated event about 4 decades ago on my sister's Datsun truck:

The rubber fuel line to the mechanical fuel pump had a pinhole, so the fuel pump could not pull a vacuum, would just suck air through the pinhole. But no fuel ever leaked out that rubber fuel line.

Funny too is that a mechanic told my sister she needed a brand new fuel pump, which she purchased, and that new one was bad, so we used the existing fuel pump after I cut off 1-inch of the bad rubber fuel line. And the parts store finally gave in and refunded my sister's money.