A properly equipped AC shop could evacuate the system. That's the only way to do it right, short of flushing all the lines. Once a vacuum is created oil can be reintroduced and refrigerant replaced. Replace the dryer (serves as filter for the system). Any moisture and debris in the system are supposed to be captured there. If you are concerned about contaminants, run for few weeks and repeat the process. Toss out the old dryer. That's should be clean enough then.

BenT
sent from my electronic leash

> On May 18, 2015, at 8:03 PM, Michael McSwain <michaelmcswain@GMAIL.COM> wrote:
> 
> Anybody have any advice on flushing an old Behr system?  Is it necessary or
> will pulling vacuum for several hours do the trick?  When I bought my van
> there was no compressor and the line ends were not sealed in any way.  So
> who knows how long it was open like that.
> 
> Thanks for any advice.
> 
> --
> m.