It's for my 91 164s, a capillary tube cracked when the engine was going back in, so it is at zero pressure. the instructions sheet from enviro-safe es12a manufacturer(?) says not to "charge into vacuum state" http://www.es-refrigerants.com/docs/31172_310.pdf
, I read that as meaning they don't recommend pulling any vacuum, except perhaps to test for leaks. Either way, it sounds like a pretty easy and painless alternative, thanks for the help!